Criminalistics: An Introduction To Forensic Science (10Th Ed.)

Front 1

How does the textbook define forensic science?

Back 1

Forensic science is the application of science to criminal and civil laws that are enforced by police agencies in a criminal justice system.

Front 2

Why is Mathieu Orfila considered “the father of forensic toxicology"?

Back 2

Orfila published the first scientific treatise on the detection of poisons and their effects on animals.

Front 3

What was Francis Galton’s principal contribution to forensic science?

Back 3

Galton undertook the first definitive study of fingerprints and developed a methodology of classifying them for filing.

Front 4

How did Calvin Goddard advance the science of firearms examination?

Back 4

Goddard was the first to use a comparison microscope to analyze bullets to determine whether they were fired from the same gun.

Front 5

What is Locard’s exchange principle?

Back 5

Locard’s exchange principle states that whenever two objects come into contact with one another, there is exchange of materials between them. When this happens during the commission of a crime, the cross-transfer of evidence can connect the suspect to his or her victim.

Front 6

What major advance in forensic science did the state of California undertake in 1972?

Back 6

In 1972 California began creating an integrated network of state-operated forensic laboratories consisting of regional and satellite facilities.

Front 7

How does the British system of forensic laboratories differ from that of the United States?

Back 7

In contrast to the American system of independent local laboratories, Britain has developed a national system of regional laboratories under the direction of the government’s Home Office.

Front 8

How has the emergence of the “fee-for-service” system affected the practice of forensic science in Great Britain?

Back 8

The fee-for-service concept has encouraged the creation of a number of private laboratories that make their services available to police and defense alike.

Front 9

List three reasons for the unparalleled growth of crime laboratories in the United
States since the 1960's.

Back 9

1. Supreme Court decisions in the 1960s required police to place greater emphasis on securing scientifically evaluated evidence and all but eliminated confessions as a routine investigative tool.
2. The dramatic increase in U.S. crime rates led to a greater need for scientific examination of criminal evidence.
3. The advent of DNA profiling led to a need for crime labs to expand their staffs and modernize their facilities to meet the demands of DNA technology.

Front 10

Describe how the structure of the U.S. federal government has affected the organization of crime labs in the United States.

Back 10

The federal system of government emphasizes the importance of retaining local control over important matters such as criminal prosecution. This has led to the growth of many local and state crime laboratories and precluded the creation of a national system. In addition, the federal government has no single law enforcement or investigative agency that has unlimited jurisdiction throughout the country.

Front 11

List three main reasons for the wide variation in total services offered by crime labs in different communities.

Back 11

1. Variations in local laws
2. Different capabilities and functions of the organization to which a laboratory is attached
3. Budgetary and staffing limitations.

Front 12

Describe the basic duties of the physical science unit in a crime lab and give three
examples of the type of work performed by a physical science unit.

Back 12

The physical science unit applies principles and techniques of chemistry, physics, and geology to the identification and comparison of crime-scene evidence. Three examples of the type of work performed by the physical science unit are drug identification, soil and mineral analysis, and examination of trace physical evidence.

Front 13

In addition to the physical science unit, what four units typically are found in full service crime labs? List at least one function performed by each of these units.

Back 13

Biology unit - Performs DNA testing, hair/fiber comparison and botanical material comparison
Firearms unit - Examines firearms, ammunition, clothing and evidence
Document examination unit - Ascertains authenticity of documents and recovers lost data
Photography unit - Examines and records physical evidence using specialized techniques to render invisible information

Front 14

List two optional units found in most crime labs and give at least one example of the type of work done by each.

Back 14

Toxicology unit - Examines body fluids and organs to determine the presence or absence of foreign substances
Latent fingerprint unit - Processes and examines evidence for latent fingerprints.

Front 15

List the main functions of the forensic scientist.

Back 15

Analyzing physical evidence;
Providing expert testimony
Furnishing training in the proper recognition, collection,
and preservation of physical evidence.

Front 16

What important principle was established in the case of Frye v. United States?

Back 16

The principle that questioned procedures, techniques, or principles must be “generally accepted” by a meaningful segment of the relevant scientific community before
they are admissible as evidence at trial.

Front 17

How did the court’s ruling in the case of Daubert v. Merrell Dow Pharmaceuticals, Inc. affect the admissibility of scientific evidence in federal courts?

Back 17

In Daubert v. Merrell Dow Pharmaceuticals, Inc., the Supreme Court asserted that “general acceptance” is not an absolute prerequisite to the admissibility of scientific evidence under the Federal Rules of Evidence. According to the Court, the Rules of Evidence assign to the trial judge the task of ensuring that an expert’s testimony rests on a reliable foundation and is relevant to the task at hand.

Front 18

How does the testimony of an expert witness differ from the testimony of a lay witness?

Back 18

A lay witness must give testimony on events or observations that arise from personal knowledge. This testimony must be factual and, with few exceptions, cannot contain the personal opinions of the witness. By contrast, the expert witness evaluates evidence that the court lacks the expertise to do, and thus must express his or her personal opinion as to the significance of the findings. The views expressed are accepted only as representing the expert’s opinion and may later be accepted or ignored in jury deliberations.

Front 19

List two ways in which a forensic odontologist can assist in criminal investigations.

Back 19

Forensic odontologists can use dental records such as X-rays, dental casts, and a photograph of a person’s smile to compare a set of dental remains and a suspected victim. A forensic odontologist can also compare bite marks left on a victim to the tooth structure of suspects.

Front 20

How does the textbook define physical evidence?

Back 20

Physical evidence is any object that can establish that a crime has been committed or can link a crime and its victim or a crime and its perpetrator.

Front 21

What is the first critical step in crime-scene investigation? Why is this step so important?

Back 21

The first critical step in crime-scene investigation is securing and isolating the crime scene. It is critical because anyone who enters a crime scene potentially could destroy physical evidence important to the investigation.

Front 22

List the three methods of crime-scene recording.

Back 22

The three methods of crime-scene recording are photography, sketches, and notes.

Front 23

What is the most important prerequisite for photographing a crime scene? Why is this so critical?

Back 23

The most important prerequisite for photographing a crime scene is for the scene to be in an unaltered condition. If objects at the scene have been removed, been added, or changed positions, the photographs may not be admissible as evidence at a trial, and their intended value will be lost.

Front 24

What is a rough sketch and what information must it accurately reflect?

Back 24

A rough sketch is a draft representation of all essential information and measurements at a crime scene. A rough sketch must accurately depict the dimensions of the crime scene as well as all recovered items of physical evidence and their exact locations.

Front 25

What information must be included in any notes taken at the crime scene?

Back 25

Crime-scene notes must include a detailed written description of the scene with the location of items of physical evidence recovered. They must also identify the time at which an item of physical evidence was discovered, by whom, how and by whom it was packaged and marked, and the disposition of the item after it was collected.

Front 26

Besides the crime scene itself, what locations must investigators search?

Back 26

The areas searched must include all probable points of entry and exit used by the criminal(s).

Front 27

What items from deceased victims must be collected and sent to a forensic laboratory?

Back 27

The following items must be sent to the forensic laboratory: the victim’s clothing, fingernail scrapings, head and pubic hairs, blood, bullets recovered from the body, hand swabs (from shooting victims), and vaginal/anal/oral swabs (in sex-related crimes).

Front 28

What is the main objective in collecting and packaging physical evidence?

Back 28

The main objective in collecting and packaging physical evidence is to prevent any change in the evidence between the time it is removed from the crime scene and the time it is received by the crime laboratory.

Front 29

What is the best way to maintain the integrity of evidence that is collected and submitted to the crime laboratory?

Back 29

The integrity of evidence is best maintained when the item is kept in its original condition as found at the crime site.

Front 30

Why is it important to package items of physical evidence in separate containers?

Back 30

Packaging evidence separately prevents damage through contact and cross contamination.

Front 31

Why should ordinary mailing envelopes not be used for packaging physical evidence?

Back 31

Ordinary mailing envelopes should not be used as evidence containers because powders and fine particles will leak out of their corners.

Front 32

Describe a druggist fold and explain why it is a superior way to package small amounts of trace evidence.

Back 32

A druggist fold consists of folding one end of a piece of paper over one-third, then folding the other end (one-third) over that, and repeating the process from the other two sides. After the paper is folded in this manner, the outside two edges are tucked into each other. A druggist fold produces a closed container that keeps the specimen from falling out.

Front 33

Why should bloodstained evidence not be stored in airtight containers? What is the best way to store such evidence?

Back 33

Bloodstained materials should not be stored in airtight containers because the accumulation of moisture in such containers may encourage the growth of mold, which can destroy the evidential value of blood. In these instances, wrapping paper, manila envelopes, and paper bags are recommended packaging materials.

Front 34

Define chain of custody and explain why maintaining a proper chain of custody is important.

Back 34

The chain of custody is a list of all people who came into possession of an item of evidence. Maintaining a proper chain of custody is the best guarantee that the evidence will withstand inquiries of what happened to it from the time of its finding to its presentation in court.

Front 35

What are the possible consequences of failing to maintain a proper chain of custody?

Back 35

Failure to substantiate the evidence’s chain of custody may lead to serious questions regarding the authenticity and integrity of the evidence and examinations of it.

Front 36

What is a standard/reference sample and why is it important to the criminalist?

Back 36

A standard/reference sample is physical evidence whose origin is known, such as blood or hair from a suspect that can be compared to crime-scene evidence. Standard/reference samples are important because they allow the criminalist to connect evidence found at the scene of a crime to the suspect and/or victim.

Front 37

What is a substrate control and why is it important?

Back 37

A substrate control consists of uncontaminated surface material close to an area where physical evidence has been deposited. A substrate control ensures that the surface on which a sample has been deposited does not interfere with the interpretation of laboratory tests.

Front 38

Why is it important to include a brief description of the case history on an evidence submission form?

Back 38

Providing a case history allows the examiner to analyze specimens in a logical sequence and make the proper comparisons, and it also facilitates the search for trace quantities of evidence.

Front 39

What two diseases have sensitized the law enforcement community to the potential health hazards that can exist at crime scenes?

Back 39

The spread of AIDS and hepatitis B have sensitized the law enforcement community to the potential health hazards that can exist at crime scenes.

Front 40

Name three basic types of protective clothing that investigators use to guard against contamination by infectious materials at a crime scene.

Back 40

Three basic types of protective clothing recommended for investigators are latex gloves, shoe covers, and liquid-repellent coveralls.

Front 41

List four situations in which a warrantless search may be justified.

Back 41

1. The existence of emergency circumstances,
2. The need to prevent the immediate loss or destruction of evidence,
3. A search of a person and property within the immediate control of the person provided it is made incident to a lawful arrest
4. A search made by consent of the parties involved.

Front 42

List six types of physical evidence derived from human or other animal sources that commonly are found at crime scenes.

Back 42

blood, semen, saliva, hair, fingerprints, organs, and physiological fluids

Front 43

List and define the two methods used by forensic scientists when examining physical evidence.

Back 43

Identification - The process of determining a substances
physical or chemical identity.
Comparison - The process of ascertaining whether two or
more objects have a common origin.

Front 44

To permit positive identification, testing procedures used by a forensic scientist must meet what two conditions?

Back 44

Testing procedures must give characteristic results
for specific standard materials as well as the number and type of tests required to positively identify a substance must be sufficient to exclude all other substances.

Front 45

Describe the two steps in the process of comparison. What question does each step attempt to answer?

Back 45

The first step in comparison is determining which properties from the suspect and standard/reference specimen to compare. This step attempts to determine whether the two samples are the same. The second step is concluding the origins of the specimens. This step attempts to determine how likely it is that two samples came from the same source.

Front 46

Define individual and class characteristics.

Back 46

Individuals characteristics - Properties of evidence that can be attributed to a common source with an extremely high degree of certainty.
Class characteristics - Properties of evidence that can be associated only with a group and never with a single source.

Front 47

Define the product rule and explain how it can be used to determine whether two blood samples come from the same source.

Back 47

The product rule states that one can obtain an overall frequency of occurrence for a genetic profile by multiplying together the frequencies of independently occurring genetic markers. If several different factors from two blood samples are found to be identical, a forensic scientist can apply the product rule to calculate how frequently blood containing that combination of factors occurs in the population. The more blood factors that match,the greater the probability that the two blood samples originated from a common source.

Front 48

What is the greatest weakness of class evidence? List two factors that contribute to this weakness.

Back 48

The greatest weakness of class evidence is that examiners cannot assign exact or even approximate probability values to the comparison of most class evidence. Few statistical data exist from which to derive comparative information for most class evidence, and society is increasingly dependent on mass-produced products that are extremely difficult to distinguish from one another.

Front 49

What is the value of class evidence? Why is this important in making a case to a jury?

Back 49

The value of class evidence lies in its ability to corroborate events with data that are, as nearly as possible, free of human error and bias. This is important because most other types of evidence (such as eyewitness testimony and confessions) are subjective in nature and susceptible to dispute, human error, or bias.

Front 50

Why are some jurists wary of allowing unconditional use of scientific evidence in court?

Back 50

Some jurists are wary about scientific evidence because juries often accord scientific evidence greater weight than other evidence, tend to consider it more trustworthy, and often view it with less skepticism. Without proper safeguards, the use of scientific evidence may unfairly prejudice a case against the accused.

Front 51

How can the extreme sensitivity of modern analytical techniques hinder the process of comparing items of physical evidence?

Back 51

When measured or examined with extreme precision, no two items—even those originating from the same source—are exactly alike. Thus, using an analytic technique that is too sensitive makes it impossible to meaningfully compare different items of evidence.

Front 52

What are IAFIS and CODIS? Describe the purpose of each.

Back 52

IAFIS is the Integrated Automated Fingerprint Identification System, a national fingerprint and criminal history database maintained by the FBI. IAFIS allows criminal investigators to compare fingerprints at a crime scene to an index of 500 million known prints. CODIS is the FBI’s Combined DNA Index System. It enables federal, state, and local crime laboratories to electronically exchange and compare DNA profiles, linking crimes to each other and to convicted offenders.

Front 53

List and describe three physical and/or chemical changes that occur in the body that enable a forensic pathologist to determine time of death.

Back 53

Rigor Mortis - Stiffening of the muscles. Occurs within 24 hours of death and disappears within 36 hours.
Livor Mortis - The settling of blood in the parts of the body closest to the ground. Creates a dark blue or purple appearance immediately and continues for up to 12 hours after death.
Algor Mortis - The cooling of the body after death. Occurs at a predictable rate, enabling the pathologist to estimate time of death from the temperature of the body.

Front 54

What important considerations must be made when determining PMI using forensic entomology?

Back 54

The time required for stage development is affected by environmental influences such as geographical location, climate, weather conditions, and the presence of drugs.

Front 55

List the areas of the skeleton that can be used to determine the gender of skeletal remains.

Back 55

The gender can be determined by observing the shape of the pelvis and sacrum, the size of the cranium, and the protrusion of the brow bone and mastoid process.

Front 56

Define the terms physical property and chemical property.

Back 56

A physical property is the behavior of a substance without alteration of the substance’s composition through a chemical reaction. A chemical property is the behavior of a substance when it reacts or combines with another substance.

Front 57

Why is the metric system of measurement easier to use than the “English system”?

Back 57

The metric system is easier to use because it employs a simple decimal relationship so that any unit of length, volume, or mass can be converted into another unit by multiplying or dividing by a factor of 10. By contrast, no simple numerical relationship exists between the various units of measurement in the English system.

Front 58

Which measuring system is used in the United States?

Back 58

The English system is used in the United States.

Front 59

List the basic units of length, mass, and volume in the metric system.

Back 59

The basic units of length, mass, and volume in the metric system are the meter, the gram, and the liter, respectively.

Front 60

What reference points are most often chosen when constructing a temperature scale?

Back 60

The most convenient reference points are the melting point of ice and the boiling point of water.

Front 61

List the two most commonly used temperature scales and their respective reference points.

Back 61

The most commonly used temperature scales are the Fahrenheit and Celsius scales. The Fahrenheit scale uses a melting point of 32° and a boiling point of 212°. The Celsius scale uses a melting point of 0° and a boiling point of 100°.

Front 62

Define weight and mass and explain the difference between the two concepts.

Back 62

Weight is a property of matter that depends on both the mass of a substance and the effects of gravity on that mass. Mass is a constant property of matter that reflects the amount of material present. Because weight depends on the force of gravity, the weight of an object can vary from one location to another. Mass differs from weight because it remains the same regardless of location.

Front 63

What is density?

Back 63

Density is a physical property of matter that is equivalent to the mass per unit volume of a substance.

Front 64

How does heat affect the density of gases and liquids?

Back 64

As the temperature of a liquid or gas increases, its density decreases.

Front 65

Define the terms refraction and refractive index.

Back 65

Refraction is the bending of a light wave as it passes from one medium to another. Refractive index is the ratio of the speed of light in a vacuum to its speed in a given substance.

Front 66

What is the difference between a crystalline solid and an amorphous solid? How does this difference affect the refractive index of each of these types of solid?

Back 66

The atoms in a crystalline solid have a regular arrangement; the atoms in an amorphous solid have no regular order. Amorphous solids have only one refractive index; crystalline solids have two refractive indices.

Front 67

Explain how a prism disperses white light into its constituent colors.

Back 67

Because each color component of light has a slightly different frequency, each color passes through the prism at a slightly different speed. This causes each color component to refract at a different angle as it emerges from the prism, thus dispersing the light into its constituent colors.

Front 68

Define intensive property and name two intensive properties of matter.

Back 68

An intensive property is a property that is not dependent on the size of an object. Intensive properties include density and refractive index.

Front 69

List two factors that make it difficult for criminalists to compare glass samples.

Back 69

Most glass evidence presented to the criminalist is either too fragmentary or too minute for the pieces to be physically reassembled or fitted together. In addition, the general chemical composition of various window glasses has so far been found to be relatively uniform among various manufacturers and thus offers no basis for identifying individual samples

Front 70

Describe the process of flotation and explain what it is used for.

Back 70

Flotation is a process used to compare the densities of glass samples. In flotation, a standard/reference glass particle is immersed in a liquid. The composition of the liquid is carefully adjusted until the glass remains suspended in the liquid. Glass chips of approximately the same size and shape as the standard/reference are then added to the liquid for comparison. If both the unknown and the standard/reference particles remain suspended in the liquid, their densities are equal to each other and to that of the liquid.

Front 71

What is the Becke line and how is it used to determine the refractive index of a glass sample?

Back 71

The Becke line is a bright halo observed near the border of a particle that is immersed in a liquid with a different refractive index. When the refractive index of the liquid is altered so that it is the same as that of the glass sample immersed in it, the Becke line disappears. This reveals the refractive index of the sample.

Front 72

What is the 3R rule and how is it applied to the analysis of glass fractures?

Back 72

The 3R rule states that Radial cracks form a Right angle on the Reverse side of the force. This rule enables an examiner to determine readily the side on which a window or pane of glass was broken.

Front 73

How can an investigator determine the order in which several successive penetrations of a glass occurred?

Back 73

It is frequently possible to determine the sequence of impacts in glass by observing the existing fracture lines and their points of termination. Each fracture always terminates at an existing line of fracture.

Front 74

How can soil evidence be valuable even if the site of the crime has not been ascertained?

Back 74

A geologist may be able to examine soil found on a victim or suspect and direct police to an area or areas where the soil originally may have been picked up. This can make it easier for the police to determine where the crime was committed.

Front 75

What is a mineral and how can minerals be important in the comparison of soil samples?

Back 75

A mineral is a naturally occurring crystalline solid that can be identified by its physical properties. The combination of minerals found in different soil or rock samples can be used to compare the samples to determine whether they have the same origin.

Front 76

What is the most important consideration when collecting soil samples from a crime scene?

Back 76

Establishing the variation of soil at the crime scene is the primary consideration when collecting soil specimens.

Front 77

At what locations should soil standard/reference samples be collected?

Back 77

Standard/reference soil samples should be collected at the site of the crime, at various intervals within a 100-yard radius of the crime scene, and at all possible alibi locations that the suspect may claim.

Front 78

Why is soil collected from suspect automobiles left in lump form?

Back 78

Soil is collected as lumps because lumps preserve a record of the buildup of several of layers of soil from different locations over time. This layering effect gives a sample greater variation, and thus makes it easier to compare the sample to soil samples found at the site of an accident.

Front 79

Define the terms element and compound and name the smallest unit of each.

Back 79

An element is a fundamental particle of matter. A compound is a pure substance composed of two or more elements. The smallest unit of an element is an atom. The smallest unit of a compound is a molecule

Front 80

Name the three forms, or states, of matter and explain how the shape and volume of matter are expressed in each state.

Back 80

The three states of matter are solid, liquid, and gas. A solid has both a specific shape and volume. A liquid has a specific volume, but takes the shape of the container in which it resides. A gas has neither a specific shape nor a specific volume.

Front 81

What physical change occurs when a substance undergoes the following changes of state: (a) from liquid to solid, and (b) from liquid to gas?

Back 81

When a substance undergoes a change of state from liquid to solid, the attractive forces between the molecules increase in strength. When a substance undergoes a change of state from liquid to gas, the attractive forces between the molecules decrease in strength.

Front 82

Define sublimation.

Back 82

Sublimation is a physical change from the solid state directly into the gaseous state.

Front 83

What happens to the attractive forces between molecules of a substance that undergo sublimation?

Back 83

Sublimation causes the attractive forces between molecules to decrease in strength.

Front 84

What is a phase and how can two different phases be distinguished from one another?

Back 84

A phase is a uniform piece of matter. Different phases are distinguished from one another by definite visible boundaries.

Front 85

What is the fundamental difference between organic and inorganic substances?

Back 85

Organic substances are based on the element carbon; inorganic substances are not.

Front 86

Describe the difference between a quantitative and a qualitative determination.

Back 86

A qualitative determination simply identifies the material in question, whereas a quantitative determination defines the percentage combination of the various components of a mixture.

Front 87

What basic tool is most often used to characterize and identify organic materials? Why is this tool chosen for that purpose?

Back 87

Spectrophotometry is the basic tool used to characterize and identify organic materials. It is used because the nature of the forces or bonds that exist between the elements in organic compounds allow scientists to readily characterize organic compounds by their absorption of light.

Front 88

What is the greatest drawback to spectrophotometry?

Back 88

Spectrophotometry requires that a material be in a relatively pure state, but the purity of physical evidence is almost always beyond the control of the criminalist.

Front 89

What technique is often employed when spectrophotometry cannot be used?

Back 89

Chromatography is often employed when spectrophotometry cannot be used to analyze physical evidence.

Front 90

Briefly describe the basic chromatographic process. Be sure to explain how motion is important to the process.

Back 90

In one form of chromatography, a questioned mixture is dissolved in liquid so that some of its molecules enter the surrounding air as gas molecules, while others remain in the liquid. During this process, the air containing the gas molecules is forced to move continuously in one direction over the liquid. If one component of the mixture has a greater percentage of its molecules in the moving (gas) phase than other components, those molecules travel over the liquid at a faster pace. When the moving phase has advanced a reasonable distance, the molecules of the different components are completely separated from one another. This allows the scientist to identify the various components in the mixture

Front 91

What three chromatographic processes are most applicable for solving analytical problems typically encountered in the crime laboratory? What is the main advantage of each?

Back 91

Gas chromatography, high-performance liquid chromatography (HPLC), and thinlayer chromatography (TLC). Gas chromatography is widely used because of its ability to resolve a highly complex mixture into its components, usually within minutes. The major advantage of HPLC is that the entire process takes place at room temperature and so it can be used to analyze sensitive materials that may be destroyed at the high temperatures experienced during gas chromatography. TLC is inexpensive and allows numerous samples to be analyzed simultaneously on one thin-layer plate.

Front 92

What is electrophoresis and what is it most widely used for?

Back 92

Electrophoresis is a technique for the separation of molecules through their migration on a support medium while under the influence of an electrical potential. Electrophoresis is widely used in the characterization of proteins and DNA in dried blood.

Front 93

What is color?

Back 93

Color is a visual indication of the fact that objects absorb certain portions of visible light and transmit or reflect others.

Front 94

What determines the color of an opaque object?

Back 94

The color of an opaque object is determined by which component color(s) of light it reflects.

Front 95

What two models do scientists use to explain the nature of light? Under what conditions does each model best describe the behavior of light?

Back 95

The first model describes light as a continuous wave; the second depicts it as a stream of discrete energy particles. When light is moving through space, its behavior can best be described as that of a continuous wave. Light as a stream of discrete particles best describes its behavior when light is absorbed by a substance.

Front 96

What is Beer’s law and what analytical technique is based on it?

Back 96

Beer’s law states that the quantity of light absorbed at any frequency is directly proportional to the concentration of material absorbing it; the more material one has, the more radiation it will absorb. Beer’s law permits spectrophotometry to be used as a technique for quantification.

Front 97

Briefly describe the basic process of spectrophotometry.

Back 97

In spectrophotometry, a beam of radiation is passed through a tube containing an unknown sample dissolved in a solution. A detector then compares the intensity of radiation passing through the solution to the intensity of a similar beam of radiation that does not pass through the solution. A signal from the detector is then fed into a recorder that produces an absorption spectrum that characterizes the sample being tested.

Front 98

What are the main strength and main weakness of ultraviolet spectrophotometry?

Back 98

The main strength of UV spectrophotometry is that the spectra it produces are very simple, which makes determining a material’s probable identity easier. The main drawback of UV spectrophotometry is that UV spectra of different substances can be similar, so the technique may not provide a definitive result.

Front 99

What major advantage does infrared spectrophotometry enjoy over ultraviolet spectrophotometry?

Back 99

Because different materials always have distinctively different infrared spectra, the IR spectrum for each substance is unique. Thus, unlike UV spectrophotometry, IR spectrophotometry can reliably identify specific substances.

Front 100

What is the most important drawback to gas chromatography?

Back 100

The most important drawback of gas chromatography is that a forensic chemist cannot identify an unknown substance based solely on the results of gas chromatography.

Front 101

In what area does mass spectrometry currently have its greatest application for forensic scientists?

Back 101

At present, mass spectrometry finds its widest application in areas relating to the identification of drugs.

Front 102

What is a trace element and why are trace elements important in analyzing physical evidence?

Back 102

A trace element is an element found in very small quantities. For the criminalist, the presence of trace elements is particularly useful because they provide markers that may establish the source of a material or at least provide additional points for comparison of two items of physical evidence

Front 103

Explain how the analysis of trace elements was important to the investigation of the assassination of President John F. Kennedy.

Back 103

Bullets recovered from Kennedy’s brain, the wrist of Governor John Connally, and the car in which both were riding at the time of the assassination were found to have almost identical concentrations of the trace elements silver and antimony. This supports the conclusion that the bullets that struck Kennedy and Connally were fired by the same shooter.

Front 104

What two characteristics of elements form the basis of the analytical techniques of emission spectroscopy and atomic absorption spectrophotometry?

Back 104

Elements selectively absorb and emit light.

Front 105

Describe the difference between a continuous spectrum and a line spectrum. Which is most helpful in identifying a particular element and why?

Back 105

A continuous spectrum shows a continuous band of colors all blending into one another. A line spectrum shows a series of lines separated by black areas in which each line represents a definite wavelength or frequency. A line spectrum is most helpful in identifying a particular element because it serves as a unique “fingerprint” of an element that differs from the spectra of all other elements.

Front 106

How does the quantity of light absorbed during atomic absorption spectrophotometry relate to the concentration of the absorbing element? What is the significance of this relationship for the forensic scientist?

Back 106

The concentration of the absorbing element is directly proportional to the quantity of the light absorbed. This allows the forensic scientist to accurately determine the concentration of a particular element in a sample.

Front 107

Why do forensic scientists often use inductively coupled plasma (ICP) emission spectrophotometry to analyze mutilated bullets?

Back 107

Mutilated bullets are often not suitable for traditional microscopic comparisons against an exemplar test-fired bullet. In such situations, ICP emission spectrophotometry can be used to obtain an elemental profile of the questioned bullet fragment for comparison against an unfired bullet generally found in the possession of the suspect.

Front 108

What is the main drawback to atomic absorption spectrophotometry?

Back 108

The main drawback to atomic absorption spectrometry is that it allows the analyst to determine only one element in a sample at a time. The forensic scientist must thus run several tests using different lamps to identify all of the elements in a sample

Front 109

What advantage does “flameless” atomic absorption enjoy over standard atomic absorption techniques?

Back 109

“Flameless” atomic absorption spectrometry is substantially more sensitive, allowing the forensic scientist to detect many elements at levels that approach onetrillionth of a gram.

Front 110

List the three basic subatomic particles and indicate whether each has positive, negative, or no electrical charge.

Back 110

Proton - Positive
Neutron - Neutral
Electron - Negative

Front 111

What is the net electrical charge of an atom? What does this indicate about the arrangement of subatomic particles in an atom?

Back 111

An atom has a net zero electrical charge, which indicates that it contains the same number of protons and electrons.

Front 112

What causes an electron to move to a higher energy level?

Back 112

An electron moves to a higher-energy orbital when it absorbs energy, such as heat or light.

Front 113

What happens when an electron moves to a lower energy level?

Back 113

When an electron moves to a lower-energy orbital, it emits energy.

Front 114

What is measured in atomic absorption spectrophotometry? How does this differ from what is measured in emission spectroscopy?

Back 114

Atomic absorption spectrophotometry measures the frequency of light absorbed by an atom when one of its electrons moves to a higher orbital. Emission spectroscopy measures the frequency of light emitted by an atom when one of its electrons moves to a lower orbital.

Front 115

What is an isotope?

Back 115

Isotopes are atoms of the same element that have different numbers of neutrons in their respective nuclei. Isotopes have different atomic mass numbers.

Front 116

List two ways in which isotopes differ from one another.

Back 116

In addition, some isotopes of an element may be very stable, while others may be quite unstable and decay rapidly.

Front 117

What causes radioactivity?

Back 117

Radioactivity is the emission of radiation that accompanies the spontaneous disintegration of unstable nuclei.

Front 118

List and define the three types of radiation.

Back 118

The three types of radiation are alpha rays, beta rays, and gamma rays. Alpha rays are a type of radiation composed of helium atoms minus their orbiting electrons. Beta rays are a form of radiation consisting of electrons. Gamma rays are a high-energy form of electromagnetic radiation.

Front 119

How does a nuclear reactor generate radioactive elements?

Back 119

In a nuclear reactor, a source of neutrons bombards the atoms of an element to create radioactive isotopes of that element. When the nucleus of an atom captures a bombarding neutron, a new isotope is formed and the nucleus is now said to be activated. Many activated nuclei immediately begin to decompose and emit radioactivity.

Front 120

Describe the process of neutron activation analysis. How does the process allow a forensic scientist to identify an isotope?

Back 120

In neutron activation analysis, a forensic scientist measures the gamma-ray radioactivity produced by a specimen that has been bombarded with neutrons. This allows the forensic scientist to identify the sample because the gamma rays of each element are associated with specific and unique energy values.

Front 121

What are the main advantage and the main weakness of neutron activation analysis?

Back 121

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Front 122

What important information about the identity of a sample cannot be determined by emission spectroscopy, atomic absorption, or neutron activation?

Back 122

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Front 123

What type of materials can be identified using X-ray diffraction? Why is this not a significant limitation when analyzing inorganic compounds?

Back 123

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Front 124

What is the main drawback to X-ray diffraction?

Back 124

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Front 125

How does a magnifying glass enlarge objects viewed through it?

Back 125

A magnifying glass makes things appear larger by refracting, or bending, light rays as they pass from the air into the glass and back into the air.

Front 126

What is the difference between a real image and a virtual image?

Back 126

A real image is an image formed when light rays converge on a surface. An observer can see a real image with the naked eye. A virtual image cannot be seen directly, but only by an observer looking through a lens.

Front 127

Why does a compound microscope produce greater magnification than a magnifying glass?

Back 127

A compound microscope produces greater magnification because it uses two lenses to enlarge the object being viewed instead of just one.

Front 128

How does the eyepiece lens contribute to magnification?

Back 128

The eyepiece lens magnifies the real, enlarged image created by the objective lens, producing a greatly enlarged virtual image of the object.

Front 129

What is vertical illumination and under what conditions would a forensic scientist use it to examine a sample? Why is it superior to transmitted illumination under such conditions?

Back 129

Vertical illumination is illumination of a specimen from above. A forensic scientist would use vertical illumination when studying opaque specimens. Transmitted illumination can be used only with specimens that are transparent.

Front 130

How does one calculate the magnification power of a compound microscope?

Back 130

The total magnification power of a compound microscope is the product of the magnifying power of each lens.

Front 131

What does numerical aperture (N.A.) measure?

Back 131

Numerical aperture measures the ability of an objective lens to resolve details into separate images instead of one blurred image.

Front 132

What is the difference between a lens with N.A. 1.0 and one with N.A. 0.5?

Back 132

A lens with N.A. 1.0 can separate details at half the distance of a lens with N.A. 0.5.

Front 133

Why might an examiner choose a microscope with a lesser magnification to study a specimen?

Back 133

An examiner might first select a lower-magnification microscope to get a good general overall view of the specimen, then switch later to a higher-power microscope to study smaller portions of the specimen in more detail.

Front 134

Briefly describe how a comparison microscope works and what it is used for.

Back 134

The comparison microscope is two compound microscopes connected by a bridge that uses mirrors and lenses to combine the images from two objective lenses into a single image. It is used to make side-by-side comparison of specimens.

Front 135

How did the comparison microscope make possible modern firearms examination?

Back 135

The comparison microscope enabled firearms examiners to compare a side-by-side magnified view of two bullets and thus to determine whether they were fired by the same gun.

Front 136

List two unique characteristics of the stereoscopic microscope.

Back 136

The stereoscopic microscope presents a three-dimensional image of an object. Also, whereas the image formed by the compound microscope is inverted and reversed, the stereoscopic microscope forms a right-side-up image.

Front 137

What is the most widely used microscope in the crime laboratory? What features make it particularly suited for examination of physical evidence?

Back 137

The stereoscopic microscope is the most frequently used microscope in the crime laboratory. Its wide field of view and great depth of focus make it an ideal instrument for locating trace evidence. Its large working distance (the distance between the objective lens and the specimen) allows for the microscopic examination of big, bulky items

Front 138

What happens to a light beam that passes through a polarizing crystal?

Back 138

beam of light passing through a polarizing crystal emerges vibrating in only one plane.

Front 139

What happens when plane-polarized light passes through a second polarizing crystal set perpendicular to the first crystal?

Back 139

When plane-polarized light passes through a second polarizing crystal set perpendicular to the first crystal, the light is blocked by the second crystal.

Front 140

What is the main advantage of the microspectrophotometer?

Back 140

The microspectrophotometer allows the forensic scientist to view a particle under a microscope while at the same time obtaining its absorption spectrum.

Front 141

Explain how the infrared microspectrophotometer determines the identity of a specimen.

Back 141

The infrared microspectrophotometer identifies a specimen by obtaining its IR spectrum, which is unique for every chemical substance.

Front 142

What type of physical evidence is the microspectrophotometer typically used to analyze?

Back 142

The technique is used to analyze fibers and paints.

Front 143

What is the basic difference between a scanning electron microscope and the other microscopes used in the crime laboratory?

Back 143

A scanning electron microscope uses a stream of electrons to create an image of the specimen being studied; all other microscopes use light coming off the specimen to create an image

Front 144

How can a scanning electron microscope be used to identify the elements present in a specimen?

Back 144

When the electron beam of the scanning electron microscope strikes a specimen, it creates X-rays that can be sorted by an X-ray analyzer. Because each element emits X-rays of characteristic energy values, the analyzer can identify the elements present in the specimen based on the energy values of the X-rays emitted by the specimen.

Front 145

How can a scanning electron microscope be used to determine whether a suspect
has recently fired a gun?

Back 145

Possible gunshot particles remaining on a shooter’s hands are lifted off with a piece of adhesive tape; the tape is then examined under the scanning electron microscope. The X-rays produced by the particles are analyzed and displayed according to their energies. This allows the examiner to detect the presence of elements frequently found in bullet primers.

Front 146

Name two physiological factors and two nondrug factors that influence drug dependence.

Back 146

Physiological factors- headaches and depression caused by withdrawal.

non-drug factors: person's expectations of the drug, societal responses or pressures to using.

Front 147

Under what class of drugs is cocaine listed according to U.S. federal drug laws? Explain why this classification is pharmacologically incorrect.

Back 147

Cocaine is listed as part of the narcotic range of drugs due to its association with socially unacceptable drugs. The drug itself is actually part of the stimulant class because it has a strong stimulant effect on the nervous system.

Front 148

What is the source of most narcotic drugs? From what plant is this substance derived?

Back 148

The source of most narcotic drugs is opium, which has a morphine content of 4-21%. It is derived from Papaver Somniferium, commonly known as poppy.

Front 149

What opium derivative is most widely used by addicts? How is it typically administered? Give two reasons why this route of administration is popular.

Back 149

The most commonly used opium derivate is heroin and is typically administered through intravenous injection. This administration route is more common both because it has a faster effect on the user and because it’s highly soluble in water which makes intravenous administration simple.

Front 150

What is the most widely used illicit drug in the United States? Under what class of drugs is it listed and what are its short-term physical and psychological effects at low to moderate doses?

Back 150

Marijuana - Schedule I

Front 151

What is the most widely abused drug in the United States? Under what class of drugs is it listed and what are its short-term physical and psychological effects at low to moderate doses?

Back 151

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Front 152

How can excessive use of depressants cause death?

Back 152

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Front 153

Name the two most commonly abused illegal stimulants and the smokable forms of each.

Back 153

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Front 154

Why does smoking provide a more intense drug experience than inhaling,or “snorting,” stimulants?

Back 154

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Front 155

Name two club drugs that are associated with drug-facilitated sexual assault, rape, and robbery. Why are these drugs relatively easy to administer to an unsuspecting victim?

Back 155

GHB and Rohypnol are central nervous system depressants that are often connected with drug-facilitated sexual assault, rape, and robbery. Both drugs are odorless, colorless, and tasteless and so will remain undetected when slipped into a drink.

Front 156

What is the most popular club drug? Name three negative health effects associated with chronic use of the drug.

Back 156

The most popular club drug is Ecstasy. Health effects associated with chronic use include seizures, muscle breakdown, stroke, kidney failure, cardiovascular system failure, and damage to the areas of the brain responsible for thought and memory.

Front 157

On what three criteria does the Controlled Substances Act classify dangerous substances?

Back 157

The Controlled Substances Act classifies dangerous substances on the basis of their potential for abuse, their potential for physical and psychological dependence, and their medical value.

Front 158

According to the Controlled Substances Act, what is the legal difference between a schedule I drug and a schedule II drug?

Back 158

Schedule I drugs have no accepted medical value in the United States; schedule II drugs may have medical use with severe restrictions.

Front 159

What is a controlled substance analog? Why are such substances considered schedule I drugs?

Back 159

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Front 160

What is a precursor?

Back 160

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Front 161

How is possession of a precursor treated under the Controlled Substances Act?

Back 161

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Front 162

List and describe the two phases in a criminalist’s scheme of action for identifying a drug.

Back 162

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Front 163

What two goals must laboratory testing accomplish to positively identify a drug?

Back 163

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Front 164

How does a color test work?

Back 164

In a color test, a chemical reagent turns a specific color when brought into contact with a particular drug.

Front 165

What is the main limitation of a color test for identifying drugs?

Back 165

The main limitation of color tests is that they are useful for screening purposes only and are never taken as conclusive identification of unknown drugs.

Front 166

Describe how a microcrystalline test works.

Back 166

In a microcrystalline test, a drop of a chemical reagent added to a small quantity of drug on a microscopic slide produces crystals that are highly characteristic of the drug.

Front 167

Name two advantages of microcrystalline tests.

Back 167

Two advantages of these tests are that they are rapid and they often do not require the isolation of a drug from its diluents.

Front 168

How are ultraviolet spectrophotometry and infrared spectrophotometry used in drug analysis?

Back 168

Ultraviolet spectrophotometry is a useful technique for establishing the probable identity of a drug. Infrared spectrophotometry is one of the few analytical techniques available to the chemist that can specifically identify a substance.

Front 169

Name two botanical features used to identify marijuana under a microscope.

Back 169

Two botanical features used to identify marijuana include short “bear claw” hairs on the upper side of the leaf and longer, non-glandular hairs on the other side.

Front 170

What method of examination is often used for marijuana when a microscopic examination cannot be obtained?

Back 170

If microscopic examination cannot be obtained, thin-layer chromatography is often used to identify marijuana.

Front 171

What is the primary duty of a forensic toxicologist?

Back 171

Forensic toxicologists detect and identify the presence of drugs and poisons in body fluids, tissues, and organs.

Front 172

What are the requirements of a suitable test for alcohol intoxication?

Back 172

Tests for alcohol intoxication must be rapid and specific; they must be designed to test hundreds of thousands of motorists annually without causing them undue physical harm or unreasonable inconvenience; and they must provide a reliable diagnosis that can be supported and defended within the framework of the legal system

Front 173

List at least three factors that determine the rate at which alcohol is absorbed into the bloodstream.

Back 173

Factors that determine the rate at which alcohol is absorbed into the bloodstream include the total time taken to consume the drink, the alcohol content of the beverage, the amount of beverage consumed, and the quantity and type of food in the stomach at the time of drinking.

Front 174

Name and describe the process by which most alcohol is eliminated from the body. How is the remaining alcohol eliminated and how is this useful in testing for alcohol?

Back 174

Nearly all of the alcohol consumed is eventually oxidized to carbon dioxide and water. The remaining alcohol is excreted unchanged in the breath, urine, and perspiration. The fact that the amount of alcohol exhaled in the breath is in direct proportion to the concentration of alcohol in the blood has led to the development of instruments that quickly, easily, and reliably measure breath for its alcohol content.

Front 175

Why is a blood test for alcohol taken shortly after drinking more advantageous for the suspect than one taken 30 minutes or more after drinking?

Back 175

The administration of a blood test for alcohol requires drawing blood from a vein, but alcohol in the veins diffuses very rapidly into body tissues during the early phases of absorption compared to blood in the arteries. Thus, blood from a vein can show a misleadingly low alcohol concentration immediately after drinking.

Front 176

What was the first successful breath-test device and what did it measure to determine blood-alcohol concentration? What is the main difference between this device and the breath-test devices currently in use?

Back 176

The first successful breath-test device was the Breathalyzer. It measured the concentration of alcohol in alveolar breath. The Breathalyzer used chemical reactions to detect the presence of alcohol, whereas most modern testing devices use infrared radiation.

Front 177

Describe how a fuel cell detector measures blood alcohol.

Back 177

In a fuel cell detector, alcohol in a suspect’s breath combines with oxygen in the air to produce acetic acid. This process generates an electrical current that is proportional to the quantity of alcohol present in the breath.

Front 178

What is the key to the accuracy of a breath tester? Describe two steps the operator
takes to ensure that this key requirement is met.

Back 178

The key to the accuracy of a breath test is to ensure that the device captures the alcohol in the alveolar breath (deep-lung breath) of the subject. This is typically accomplished by programming the unit to accept a minimum amount of breath (no less than 1.5 liters) from the subject. Also, the subject must blow for a minimum time with a minimum breath flow rate.

Front 179

What is a divided-attention task? Name and describe two divided-attention tasks often administered during field sobriety tests.

Back 179

A divided-attention task tests a subject’s ability to comprehend and execute two or more simple instructions at one time. The walk and turn test requires the suspect to walk a straight line, touching heel to toe for nine steps, then turn around on the line and repeat the process. The one-leg stand requires the suspect to stand on one foot while holding the other foot several inches off the ground for 30 seconds and simultaneously counting out loud

Front 180

What is horizontal gaze nystagmus and how does the test for it reveal blood-alcohol levels?

Back 180

Horizontal gaze nystagmus is an involuntary jerking of the eye as it moves to the side. The subject is asked to follow an object with his or her eye as far to the side as the eye can go. The higher a person’s blood-alcohol concentration, the less the eye has to move toward the side before jerking or nystagmus begins.

Front 181

What substances are typically added to blood that is collected from a subject before it is sent to a toxicology lab, and why are they added?

Back 181

An anticoagulant usually is added to blood collected from a subject to prevent it from clotting. A preservative is also added to inhibit the growth of microorganisms capable of destroying alcohol in the blood.

Front 182

Why is it best to collect blood samples from different body sites for post-mortem alcohol determination?

Back 182

It is best to collect a number of blood samples from different body sites because ethyl alcohol may be generated in a deceased individual as a result of bacterial action.

Front 183

At what blood-alcohol level is a typical driver in the United States considered legally intoxicated?

Back 183

A typical driver in the United States is considered legally intoxicated at a blood alcohol level of 0.08 percent.

Front 184

At what blood-alcohol level is a commercial truck or bus driver in the United States considered legally intoxicated?

Back 184

A commercial truck or bus driver in the United States is considered legally intoxicated at a blood-alcohol level of 0.04 percent.

Front 185

List two significant challenges a forensic toxicologist faces when attempting to identify drugs present in a body.

Back 185

The forensic toxicologist often has no clue as to which drug or drugs may be present. Also, by the time a drug specimen reaches the toxicology laboratory, it has been dissipated and distributed throughout the body, so the toxicologist must work with very small amounts of drugs.

Front 186

What is metabolism and how does it complicate the task of the forensic toxicologist?

Back 186

Metabolism is the process by which the body changes one chemical to another in order to facilitate its elimination from the body. Because of metabolism, few substances enter and completely leave the body in the same chemical state.

Front 187

Why is it necessary to follow a positive screening test for drugs with a confirmation test? What is the confirmation test of choice?

Back 187

A follow-up test is required after a positive screening test to ensure that the positive result was not caused by a substance with a chemical structure similar to that of an illegal drug. Gas chromatography/mass spectrometry is generally accepted as the confirmation test of choice.

Front 188

What is the A-B-O system? Why is the system no longer used by forensic scientists?

Back 188

The A-B-O system is a system for classifying blood according to general groups or types. Forensic scientists no longer use it because DNA identification has replaced the A-B-O system as the most accurate means of linking blood evidence to an individual.

Front 189

What is an antigen and how is it useful in individualizing blood?

Back 189

An antigen is a substance, usually a protein, that stimulates the body to produce antibodies against it. The surface of every blood cell contains antigens that can be grouped into systems depending on their relationship to one another. The combination of antigens on blood cells serves as a basis for comparing blood samples.

Front 190

What is an antibody and what happens when an antibody reacts with its specific antigen?

Back 190

An antibody is a protein that destroys or inactivates a specific antigen. When an antibody reacts with its specific antigen the two immediately combine, causing the antibody to attach itself to the blood cell containing the antigen.

Front 191

What factor is most whole blood typed for?

Back 191

Most whole blood is typed for its A-B-O identity.

Front 192

What is the most common blood type in the United States? Which is least common?

Back 192

Type O blood is the most common in the United States; type AB is the least common.

Front 193

For what other application do forensic scientists often use specific antigen–antibody reactions?

Back 193

Specific antigen–antibody reactions are used to detect drugs in blood and urine.

Front 194

What is the EMIT technique frequently used for, and what is its greatest limitation?

Back 194

One of the most frequent uses of the EMIT technique in forensic laboratories has been for screening the urine of suspected marijuana smokers. The greatest problem associated with the technique is determining when the individual actually used marijuana.

Front 195

What is the difference between monoclonal and polyclonal antibodies? Which type are more useful for the forensic scientist and why?

Back 195

Monoclonal antibodies bind to only one specific antigen site; polyclonal antibodies can bind to a number of different sites on an antigen. Monoclonal antibodies are more useful because they can be used to create antigens for specific substances that the forensic scientist may need to test for, such as illegal drugs.

Front 196

What three questions must the criminalist be prepared to answer when examining dried blood?

Back 196

1. Is it blood?
2. From what species did the blood originate?
3. If the blood is of human origin, how closely can it be associated with a particular individual?

Front 197

List two commonly used color tests for blood. How does a luminol test differ from these tests?

Back 197

Two commonly used color tests for blood are the Kastle-Meyer test and the Hemastix test. Luminol testing differs from these techniques because the reaction of luminol with blood results in the production of light rather than color.

Front 198

What is the purpose of a precipitin test?

Back 198

A precipitin test is used to determine whether a bloodstain is of human or animal origin.

Front 199

Name three strengths of precipitin tests.

Back 199

1. It is very sensitive
2. It requires only a small amount of blood for testing
3. Human bloodstains dried for years may still give a positive reaction.

Front 200

What is a genotype?

Back 200

A genotype is the particular combination of genes present in the cells of an individual.

Front 201

How do parents’ genotypes affect the blood type of their offspring? In what area of the law does this information have important implications?

Back 201

Because each parent passes its genes to its offspring, and blood type is determined by genes, a child cannot have a gene for a blood type that does not appear in either of its parents. This fact has important implications in resolving cases of disputed paternity.

Front 202

What is acid phosphatase and how is it used by forensic scientists?

Back 202

Acid phosphatase is an enzyme that is secreted by the prostate gland into seminal fluid. It is used by forensic scientists to determine the presence of semen in a stain.

Front 203

List three reasons why spermatozoa are often not found in seminal fluid collected at a crime scene.

Back 203

1. Spermatozoa bind tightly to cloth materials such as underwear
2. Spermatozoa are extremely brittle when dry and easily disintegrate if the stain is washed or rubbed;
3. Sexual crimes may involve males who have an abnormally low—or even zero—sperm count.

Front 204

Why is it important for investigators to seek information about when and if voluntary sexual activity last occurred before a sexual assault?

Back 204

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Front 205

What is complementary base pairing?

Back 205

Complementary base pairing is the specific pairing of adenine with thymine and cytosine with guanine in DNA.

Front 206

What is the importance of the order in which base pairs are arranged?

Back 206

The order in which base pairs are arranged defines the role and function of a DNA molecule.

Front 207

How are proteins formed?

Back 207

Proteins are formed by linking a combination of amino acids.

Front 208

What determines the shape and function of a protein?

Back 208

The sequence of amino acids in a protein chain determines the shape and function of the protein.

Front 209

List three advantages gained from decoding the human genome.

Back 209

Decoding the human genome can be useful for diagnosing and treating genetic diseases; it is crucial for understanding the underlying causes of cancer; and comparing the human genome with that of other organisms will help us understand the role and implications of evolution.

Front 210

Describe the process of DNA replication.

Back 210

DNA replication begins with the unwinding of the DNA strands in the double helix. Each strand is then exposed to a collection of free nucleotides. The double helix is re-created as the nucleotides are assembled in the proper order (A with T and G with C).

Front 211

What is the importance of DNA replication?

Back 211

The result is the emergence of two identical copies of DNA. DNA replication allows a cell to pass on its genetic identity when it divides.

Front 212

What is polymerase chain reaction (PCR) and how is it useful to forensic scientists?

Back 212

PCR is a technique for replicating or copying a portion of a DNA strand outside a living cell. The ability to multiply small bits of DNA with PCR means that sample size is no longer a limitation for the forensic scientist attempting to characterize DNA recovered from crime-scene evidence.

Front 213

What are tandem repeats and how are they useful to the forensic scientist?

Back 213

Tandem repeats are regions of a chromosome that contain multiple copies of a core DNA sequence arranged in a repeating fashion. Tandem repeats are useful for the forensic scientist because they provide a way to distinguish one individual from another through DNA typing.

Front 214

What are short tandem repeats (STRs) and what are their significance to DNA typing?

Back 214

STRs are locations (loci) on the chromosome that contain a short sequence core that repeats itself within the DNA molecule and that serve as helpful markers for identification.

Front 215

List two advantages STRs have over restriction fragment length polymorphisms (RFLP).

Back 215

1. The shorter DNA strands found in STRs are likely to be more stable and less subject to degradation
2. STRs can be amplified by PCR

Front 216

What is multiplexing and why is it used in DNA profiling?

Back 216

Multiplexing is a technique that simultaneously detects more than one STR in a single DNA analysis. Multiplexing is important to DNA profiling because the more STRs a forensic scientist can characterize, the greater the likelihood that they originated from the same individual.

Front 217

What characteristics are revealed by the amelogenin gene and Y-STRs?

Back 217

The amelogenin gene can reveal the sex of the person who contributed a DNA sample. Y-STRs are male specific and are useful for characterizing multiple-male DNA mixtures.

Front 218

What are the three main differences between nuclear DNA and mitochondrial DNA?

Back 218

Nuclear DNA is found only in the nucleus of the cell, is arranged in a continuous strand of bases, and is contributed by both parents. Mitochondrial DNA (mtDNA) is found outside the nucleus of the cell, is arranged in a circular loop of bases, and is contributed only by the mother.

Front 219

Name two advantages of mitochondrial DNA analysis compared to nuclear DNA analysis.

Back 219

1. Mitochondrial DNA is much more abundant in the body than is nuclear DNA
2. mtDNA analysis is significantly more sensitive than nuclear DNA profiling

Front 220

Name two disadvantages of mitochondrial DNA analysis compared to nuclear DNA analysis.

Back 220

1. Individuals of the same maternal lineage are indistinguishable by mtDNA analysis
2. mtDNA typing does not approach STR analysis in its discrimination power

Front 221

How should packages containing DNA evidence be stored? Name one common exception and explain why it should be handled differently and how it should be stored.

Back 221

All packages containing DNA evidence should be refrigerated or stored in a cool location out of direct sunlight until delivery to the laboratory. One common exception is blood mixed with soil. Microbes present in soil rapidly degrade DNA, so blood in soil must be stored in a clean glass or plastic container and immediately frozen

Front 222

List four steps an investigator should take to prevent contamination of DNA evidence.

Back 222

1. Change gloves before handling each new piece of evidence
2. Collect a substrate control for possible subsequent laboratory examination
3. Pick up small items of evidence such as cigarette butts and stamps with clean forceps
4. Package each item of evidence in its own well-ventilated container.

Front 223

How is the hair cuticle used to identify different animal species?

Back 223

The cuticle is formed by overlapping scales that occur in a variety of patterns in different animal species.

Front 224

What aspect of the hair cortex is most important for the criminalist and why?

Back 224

The cortex derives its major forensic importance from the fact that it is embedded with the pigment granules that impart hair with color. The color, shape, and distribution of these granules provide the criminalist with important points of comparison among the hairs of different individuals.

Front 225

What is the follicular tag and why is it important to forensic scientists studying hair?

Back 225

The follicular tag is a translucent piece of tissue surrounding the hair’s shaft near the root. It contains the richest source of DNA associated with a hair.

Front 226

In comparing two hair samples, what aspects of the hair is the criminalist particularly interested in matching? What other features of hair are important to compare?

Back 226

In comparing hair, the criminalist is particularly interested in matching the color, length, and diameter. Other important features to compare are the presence or absence of a medulla and the distribution, shape, and color intensity of the pigment granules in the cortex.

Front 227

Which of the following cannot be confidently determined by a microscopic examination of hair: age, sex, racial origin, the part of the body from which the hair came, or whether the hair was pulled out or fell out?

Back 227

Sex and Age

Front 228

Why are most hair specimens collected at crime scenes not good sources of DNA?

Back 228

Most in hair specimens are in the telogen stage because they contain the least amount of DNA

Front 229

What type of hair specimens are potentially the richest source of nuclear DNA and why?

Back 229

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Front 230

What is mitochondrial DNA and why is it useful in analyzing hair samples?

Back 230

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Front 231

List three important considerations when submitting hair samples to a crime laboratory.

Back 231

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Front 232

How has mass production limited the value of fiber evidence?

Back 232

Many goods are made from almost identical fibers, making it difficult to provide individual identification of specific fibers with any degree of certainty.

Front 233

What is the first and most important step in the examination of fiber?

Back 233

The first and most important step in the examination is a microscopic comparison for color and diameter using a comparison microscope.

Front 234

What physical characteristics of fiber might help an examiner identify it?

Back 234

Other features that could aid in comparison are lengthwise striations on the surface of some fibers and the pitting of the fiber’s surface with particles added in the manufacturing process to reduce shine. The cross-sectional shape of a fiber may also help characterize the fiber.

Front 235

How can microspectrophotometry and chromatography be used to analyze fiber evidence?

Back 235

Microspectrophotometry can be used to compare the colors of fibers through their spectral patterns. Using chromatography, the forensic scientist can separate the constituents of dyes found in two fabric samples and compare them for similarity

Front 236

Name two analytical devices used by forensic scientists to determine the class of a fiber.

Back 236

The polarizing microscope and the infrared microspectrophotometer are both used to determine the class of a fiber.

Front 237

How does the way most automobile manufacturers paint their cars help in the forensic comparison of automobile paint?

Back 237

Manufacturers apply a variety of coatings to the body of an automobile, which adds significant diversity to automobile paint.

Front 238

What three features of paint does a forensic scientist compare using a microscope?

Back 238

1. Color
2. Surface texture
3. Color layer sequence.

Front 239

Why is layer structure important for evaluating the significance of paint evidence?

Back 239

When paint specimens possess colored layers that match in number and sequence of colors, the examiner can begin to think confidently in terms of relating the paints to a common origin.

Front 240

What is the greatest shortcoming in using layer structure to analyze paint evidence?

Back 240

The shortcoming of analysis of paint layer structures is that most paint specimens presented to the criminalist do not have a layer structure sufficiently complex to allow individualization to a single source.

Front 241

How is pyrolysis gas chromatography used to distinguish one paint binder formulation from another?

Back 241

In pyrolysis gas chromatography, heat is used to break apart the chain of polymers that make up the paint binder. The decomposed products of the polymer are swept through a gas chromatograph, which records a pattern of the separated products of the polymer.

Front 242

What is PDQ and how is it used in identifying paint samples?

Back 242

PDQ (Paint Data Query) is a computerized database maintained by the Royal Canadian Mounted Police Forensic Laboratories that contains information about automotive paint layer colors, primer colors, and binder composition. PDQ allows an analyst to obtain information on paints related to automobile make, model, and year.

Front 243

Where is most paint evidence likely to be found?

Back 243

Paint evidence is most likely to be found on or near people or objects involved in hit-and-run incidents.

Front 244

Why is it important that paint evidence from a hit-and-run accident be collected close to the area of the car that was suspected of being in contact with the victim?

Back 244

Because other portions of the car may have faded or been repainted.

Front 245

List three factors that make investigating arson and explosions particularly difficult for forensic scientists.

Back 245

1. Arson and explosion incidents are committed at the convenience of a perpetrator who has thoroughly planned the act
2. The perpetrator has left the scene long before an investigation is launched
3. The extensive destruction that frequently dominates the crime scene makes it more difficult to obtain proof of the commission of the offense.

Front 246

What happens to the atoms of a molecule that undergoes a chemical reaction?

Back 246

In a chemical reaction, the atoms of a molecule are rearranged to form new substances, or products.

Front 247

How is energy consumed in a chemical reaction?

Back 247

Energy is consumed in a chemical reaction when the bonds holding the atoms of the original molecules together are broken.

Front 248

How is energy released in a chemical reaction?

Back 248

Energy is released when the bonds between atoms re-form to create new products as a result of the reaction.

Front 249

What is the energy barrier and how does it relate to the concept of ignition temperature?

Back 249

The energy barrier is the minimum amount of energy required to initiate a chemical reaction. Ignition temperature is the minimum temperature at which a fuel spontaneously ignites. Thus, the energy barrier for any fuel is directly related to its ignition temperature.

Front 250

How does the speed of an oxidation reaction affect its ability to produce a flame?

Back 250

The faster an oxidation reaction takes place, the greater the likelihood it will produce a flame.

Front 251

What factors influence the speed of the reaction?

Back 251

Factors that influence the speed of the reaction include the physical state of the fuel and the temperature.

Front 252

What physical state must a fuel occupy in order to produce a flame? Why can it produce a flame only in this state?

Back 252

Fuel must be in a gaseous state to produce a flame, because only in the gaseous state can its molecules collide frequently enough to support a flaming fire.

Front 253

Define and describe the process of pyrolysis.

Back 253

Pyrolysis is the decomposition of organic matter by heat. In pyrolysis, heat causes solid organic matter to decay. This generates gaseous products that can combine with oxygen to produce a fire. The heat from the fire pyrolyzes more solid fuel into volatile gases, which sustains the fire.

Front 254

What are oxidizing agents and why are they used in explosives?

Back 254

An oxidizing agent is a substance that supplies oxygen to a chemical reaction. An explosion occurs so rapidly that oxygen in the air cannot participate in the reaction. For this reason, many explosives must have their own source of oxygen in order to produce the chemical reaction necessary to create an explosion.

Front 255

Why is it important that the arson investigator begin examining a fire scene for signs of arson as soon as the fire has been extinguished?

Back 255

Most arsons are started with petroleum-based accelerants that may evaporate within a matter of days or even hours.

Front 256

What is the primary focus of a fire-scene search and why?

Back 256

A search of the fire scene must focus on finding the fire’s origin, because this area will prove most productive in any search for an accelerant or ignition device.

Front 257

What evidence at a fire site may indicate the possibility of arson?

Back 257

Some telltale signs of arson include evidence of separate and unconnected fires; use of “streamers”—such as a trail of gasoline or paper—to spread the fire from one area to another; the presence of containers capable of holding an accelerant; finding a potential ignition device; and the existence of an irregular-shaped pattern on a floor or on the ground caused by pouring an accelerant onto the surface.

Front 258

Where will an investigator usually locate the probable point of origin of a fire?

Back 258

The probable origin of a fire will most likely be located closest to the lowest point that shows the most intense characteristics of burning.

Front 259

What factors can cause a fire to deviate from normal behavior?

Back 259

Factors that can cause a fire to deviate from normal behavior include prevailing drafts and winds; secondary fires caused by collapsing floors and roofs; the physical arrangement of the burning structure; stairways and elevator shafts; holes in the floor, wall, or roof; and the effects of the firefighters in suppressing the fire

Front 260

Why are some traces of the accelerants used in an arson usually found even after intense fires?

Back 260

When an accelerant is poured over a large area, some of it is likely to seep into porous surfaces such as cracks in the floor, upholstery, rags, plaster, wallboards, and carpet, where enough of it remains unchanged that it can be detected in the crime laboratory.

Front 261

Why might an investigator conduct laboratory tests on unburned control material collected from a fire scene?

Back 261

Laboratory tests may be made on unburned control material to analyze the breakdown products caused by the material’s exposure to intense heat during the fire.

Front 262

Describe the headspace technique for recovering accelerant residues.

Back 262

In the headspace technique, an airtight container holding debris from the fire scene is heated, vaporizing any volatile residue present in the debris and trapping the vapor in the container’s enclosed airspace. The vapor, or headspace, is removed with a syringe.

Front 263

What instrument is most often used to detect and characterize recovered flammable residues?

Back 263

A gas chromatograph is usually used to detect and characterize residues in the vapor.

Front 264

What produces the violent physical disruption of the surrounding environment released in an explosion? Explain how this creates shrapnel when a bomb explodes.

Back 264

The sudden buildup of expanding gas pressure at the origin of an explosion produces the violent physical disruption of the surrounding environment. In a bomb, the extremely high pressure caused by the expanding gases pushes on the walls of the bomb, stretching and finally shattering them. The pieces of the walls are shattered and thrown outward in all directions by the force of the explosion, creating shrapnel.

Front 265

What is an oxidizing agent?

Back 265

An oxidizing agent is a chemical that supplies oxygen to a reaction.

Front 266

Why is an oxidizing agent important to an explosion?

Back 266

Oxidizing agents are important to explosions because detonation occurs so rapidly that oxygen in the air cannot participate in the reaction; thus, many explosives must have their own source of oxygen.

Front 267

What characteristic of an explosive determines whether it is classified as a low explosive or a high explosive? How is this reflected in the type of pressure wave produced by the explosive?

Back 267

The speed at which an explosive decomposes determines its classification as a low or high explosive. Low explosives produce a subsonic pressure wave, whereas high explosives produce a supersonic pressure wave.

Front 268

Name two types of low explosives and list the ingredients of each.

Back 268

Black powder - potassium nitrate, carbon, and sulfur
Smokeless powder - nitrocellulose and either nitroglycerin or nitrated cotton.

Front 269

Why does black powder not explode unless it is ignited in a confined area? What practical application besides explosives does this make black powder suitable for?

Back 269

Black powder does not explode when unconfined because it decomposes too slowly. This makes black powder suitable for use in safety fuses, in which it carries a flame to an explosive charge.

Front 270

What are primary explosives and what are they used for?

Back 270

A primary explosive is a high explosive that is easily detonated by heat or shock. They are used to detonate the most commonly used high explosives, which are known as secondary explosives.

Front 271

What is a detonator?

Back 271

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Front 272

What is the most common form of detonator?

Back 272

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Front 273

What role does ammonium nitrate play in water gels, emulsions, and ANFO explosives?

Back 273

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Front 274

In what commercial form can ammonium nitrate be readily obtained?

Back 274

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Front 275

In what liquid does a forensic scientist rinse debris recovered from an explosion site and why?

Back 275

A forensic scientist rinses debris from an explosion site in acetone because most explosives are highly soluble in acetone. This allows the scientist to quickly remove any traces of explosive from the debris so they can be isolated and identified.

Front 276

What type of materials can be identified using X-ray diffraction?

Back 276

X-ray diffraction can be applied only to the study of solid, crystalline materials— that is, solids whose atoms have a definite and orderly arrangement.

Front 277

What are taggants and how are they used to identify explosives?

Back 277

Taggants are tiny color-coded chips added to commercial explosives during the manufacturing process. Some of these chips would be expected to survive an explosion and be recovered at explosion scenes. The taggants in an explosive are arranged in a color sequence that indicates where the explosive was made and when it was produced

Front 278

Who published the first book on the science of fingerprinting? What were the book’s most important contributions to understanding fingerprints?

Back 278

Francis Galton published the first book on the subject of fingerprinting. The book’s most important contributions were to demonstrate that no two prints are identical and that an individual’s prints remain unchanged from year to year.

Front 279

What major advance in fingerprint technology was pioneered by Juan Vucetich and Sir Richard Henry? What was the importance of this advance?

Back 279

Vucetich and Henry pioneered the creation of classification systems capable of filing many thousands of prints in a logical and searchable sequence. This allowed law enforcement officials to quickly compare prints found at a crime scene to those of known criminals as an aid to identifying potential suspects.

Front 280

What aspect of a fingerprint determines its individuality?

Back 280

The identity, number, and relative location of ridge characteristics impart individuality to a fingerprint.

Front 281

What is the dermal papillae and why is it important in fingerprinting?

Back 281

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Front 282

Why is it almost impossible to obscure one’s fingerprints by surgery or mutilation?

Back 282

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Front 283

Describe each of the three classes of fingerprints. Which class is the most common in the population? Which is least common?

Back 283

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Front 284

What aspect of a fingerprint forms the basis for primary classification under the FBI system?

Back 284

The presence or absence of the whorl pattern is the basis for determining the primary classification in the FBI system.

Front 285

What is the main drawback of the FBI fingerprinting system?

Back 285

The main drawback of the FBI system is that it is useful only when a full set of fingerprints is available.

Front 286

Briefly describe how the Automated Fingerprint Identification System (AFIS) creates a fingerprint image.

Back 286

AFIS scans fingerprints and converts them into digital images that contain data on the relative location and orientation of ridge characteristics.

Front 287

What characteristics of the fingerprint does the AFIS record for comparison?

Back 287

The system records the points where ridges terminate, the points where they branch into two ridges, and the relative position and orientation of each ridge characteristic.

Front 288

What is the final step in fingerprint identification? Why is this step necessary if a computerized database of fingerprints is available to the forensic scientist?

Back 288

The final step in fingerprint identification is always visual comparison of the prints in question by a trained examiner. A computer database can only produce a list of prints that are similar to the print in question; it cannot make a positive identification.

Front 289

List and describe the three types of fingerprints that may be found at a crime scene.

Back 289

Visible prints are made when a finger deposits a visible material such as ink, dirt, or blood onto a surface. Plastic prints are ridge impressions left on a soft material such as putty, wax, soap, or dust. Latent or invisible prints are impressions caused by the transfer of body perspiration or oils present on finger ridges to the surface of an object.

Front 290

List two types of specialized fingerprint powders and name one advantage each has over traditional fingerprint powder.

Back 290

Two specialized fingerprint powders are magnetic-sensitive powder and fluorescent powder. Using magnetic-sensitive powder offers less chance that the print will be destroyed or damaged because the powder is spread using a magnetic brush that has no bristles to come in contact with the surface containing the print. Fluorescent powders reveal a vivid image of a print under ultraviolet light. When the developing print is photographed under UV light, the color of the surface will not obscure the print

Front 291

What is the most commonly used chemical method to visualize latent fingerprints on porous materials? If this method is unsuccessful, what other technique typically
is used?

Back 291

The ninhydrin method is most commonly used to visualize latent fingerprints on porous materials. If the ninhydrin method fails, the Physical Developer technique typically is used.

Front 292

What phenomenon underlies many of the new chemical techniques used to visualize latent fingerprints? Why is this phenomenon so valuable in fingerprint visualization?

Back 292

The phenomenon of fluorescence serves as the underlying principle of many of the new chemical techniques used to visualize latent fingerprints. Substances that emit light or fluoresce are more readily seen either with the naked eye or through photography as compared to non-light-emitting materials.

Front 293

When should a fingerprint be “lifted” from a crime scene?

Back 293

A print should be “lifted” from a crime scene when it is on a large, immovable object.

Front 294

Describe how to lift and preserve a fingerprint using adhesive tape.

Back 294

Dust the print with fingerprint powder, then cover the print with adhesive tape. When the tape is pulled up, the powder is transferred to the tape. Then the tape is placed on a card that provides a good background contrast with the powder.

Front 295

What is digital imaging and how is it used in fingerprint analysis?

Back 295

Digital imaging is a process through which a picture is converted into a series of square electronic dots known as pixels. It is used to compare fingerprints and to enhance poor fingerprint images.

Front 296

What is the greatest limitation to digital imaging?

Back 296

The main limitation of digital imaging is that it is only as useful as the images it has to work with.

Front 297

List three class characteristics of a gun barrel.

Back 297

Three class characteristics of a gun barrel are its caliber, the number of lands and grooves, and the direction and twist of the lands and grooves.

Front 298

Describe how a firearms examiner compares two bullets.

Back 298

The examiner places both bullets under a comparison microscope, pointing in the same direction, and then rotates one bullet until a well-defined land or groove comes into view. When the examiner locates striation markings on this bullet, the other bullet is rotated until a matching region is found. When a matching area is located, the two bullets are simultaneously rotated to locate additional matching areas around the periphery of the bullets.

Front 299

What characteristic does an examiner most often use to identify bullets and why?

Back 299

The examiner uses the striation markings to identify bullets because no two rifled barrels have identical striation markings.

Front 300

List two reasons why striations on bullets fired from the same gun may vary slightly.

Back 300

The presence of grit and rust can alter the markings on bullets fired through the same barrel. Striation markings on a barrel are not permanent structures; they are subject to continuing change and alteration through wear as succeeding bullets traverse the length of the barrel.

Front 301

Besides the barrel, what parts of a firearm may leave distinctive markings on a shell cartridge?

Back 301

The firing pin, the breechblock, the extractor, the ejector, the magazine, the clip, and the fire chamber walls may all leave distinctive markings on a shell casing.

Front 302

Why does a firearms examiner test-fire bullets from a suspect barrel?

Back 302

The examiner must test-fire bullets through the suspect barrel because there is no other practical way to directly compare the markings on the fired bullet and those found within a barrel.

Front 303

What is distance determination?

Back 303

The examiner must test-fire bullets through the suspect barrel because there is no other practical way to directly compare the markings on the fired bullet and those found within a barrel.

Front 304

Describe two situations in which distance determination can establish the facts of a shooting incident.

Back 304

If a suspect pleads self-defense as the motive for a shooting, determining how far apart the suspect and victim were at the time of shooting can establish the facts of the incident. Distance determination can also determine whether a shooting was suicide

Front 305

What evidence does an investigator study to make a distance determination?

Back 305

The distribution of gunpowder particles and other discharge residues around the bullet hole permits an assessment of the distance from which a handgun or rifle was fired.

Front 306

How can test-firing a suspect weapon help the investigator make a distance determination?

Back 306

By comparing residue patterns from test firings to those found at the crime scene, the examiner may find enough similarity in shape and density on which to base an opinion as to the distance from which the shot was fired.

Front 307

List three characteristics of a bullet hole that indicate that the shot was fired at extremely close range.

Back 307

1. A heavy concentration of smokelike vaporous lead usually surrounds the bullet entrance hole
2. Loose fibers surrounding a contact hole show scorch marks from the flame discharge of the weapon, and some synthetic fibers show signs of being melted as a result of the heat from the discharge. 3. The blowback of muzzle gases may produce a stellate (star-shape) tear pattern around the hole.

Front 308

What is the Greiss test and what two pieces of information can it provide to an investigator?

Back 308

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Front 309

How is shot pattern used to make a distance determination for shotgun blasts?

Back 309

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Front 310

What factors other than distance to target can affect the distance determination?

Back 310

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Front 311

What evidence do investigators look for when trying to determine whether a suspect has fired a handgun?Where is such evidence typically found and why?

Back 311

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Front 312

Why does analysis of primer residue from a suspect’s hands produce a low rate of positive results?

Back 312

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Front 313

Why is such analysis typically ineffective in locating primer residue from a .22-caliber gun?

Back 313

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Front 314

Describe how a criminalist restores an obliterated serial number on a weapon.

Back 314

To restore an obliterated serial number, the criminalist applies a suitable etching agent to the area that has been defaced. The metal in this area dissolves at a faster rate than the unaltered metal surrounding it, thus permitting the etched pattern to appear in the form of the original numbers.

Front 315

Why would an investigator not pick up a weapon by its barrel with a pencil or stick in order to protect latent fingerprints? How should suspect firearms be handled in such a situation?

Back 315

An investigator would not pick up a weapon by its barrel with a pencil or stick in order to protect fingerprints because this may disturb powder deposits, rust, or dirt lodged in the barrel, and consequently may alter the striation markings on test-fired bullets. If the recovery of latent fingerprints is a primary concern, it is best to hold the weapon by the edge of the trigger guard or by the checkered portion of the grip.

Front 316

What characteristics of a suspect firearm should an investigator record before unloading it?

Back 316

The investigator should record the weapon’s hammer and safety position as well as the location of all fired and unfired ammunition in the weapon.

Front 317

Why should the investigator number the chambers and cartridges when unloading a suspect weapon?

Back 317

The cylinders and cartridges should be numbered because this information may be useful to determine the sequence of events, particularly in cases in which several shots were fired.

Front 318

What is the investigator’s primary concern when collecting and handling bullets and cartridge cases?

Back 318

The protection of class and individual markings on bullets and cartridge cases must be the primary concern of the field investigator who is handling such evidence.

Front 319

Why must the investigator exercise extreme caution when removing a bullet lodged in a wall or other object?

Back 319

If the bullet’s surface is accidentally scratched when removing it from a wall or other object, valuable striation markings could be obliterated that can help link the bullet to a suspect weapon.

Front 320

Name two types of marks that impart individuality to a tool and explain how the marks are made.

Back 320

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Front 321

What techniques does an investigator use to analyze tool marks that cannot be removed from a crime scene? What is the disadvantage of this technique?

Back 321

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Front 322

What is the first thing the investigator does before handling or moving any impression at a crime scene? Why is this considered merely a backup or precautionary procedure?

Back 322

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Front 323

What kinds of impression evidence might a forensic odontologist be asked to analyze? How might this help identify a suspect?

Back 323

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