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81 Cards in this Set

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What is a real image?

Image formed by actual convergence of light rays on a screen

What is a virtual image?

Image that cannot be seen directly, only by viewer looking through a lens

What is reflected light?

Light from above the specimen, used mostly for opaque specimens

What is transmitted light?

Light passing up from the condenser and through the specimen

What is the base?

Supports the microscope

What is the arm?

C-shaped, supports microscope and acts as handle

What is the stage?

Where the specimens are placed, holds glass slides in place with spring clips

What is the body tube?

Cylindrical tube on which objective and eyepiece lenses are mounted, serves as corridor for light

What is the coarse adjustment?

Knob that focuses microscope lens on specimen by raising and lowering the body tube

What is the fine adjustment?

Moments similar to those of the coarse adjustment, but on a smaller magnitude

What is the illuminator?

Light from a bulb to pass through the condenser

What is the condenser?

Collects light rays from base illuminator to concentrate light through specimen

What is an objective lens?

Lens positioned closest to specimen, several lenses also mounted on revolving nosepiece

What is an eyepiece or ocular lens?

Lens closest to eye

What is field of view?

Area of a specimen that can be seen after being magnified

What is depth of focus?

Thickness of a specimen that is entirely in focus under a microscope

What are the advantages of a stereoscopic microscope?

1) Creates 3D image of specimen


2) Allows for right-side-up image


3) Wide field of view


4) Greater depth of focus


5) Larger working distance

What is working distance?

Distance between the objective lens and specimen

How do the mechanisms of image formation of light microscopes differ from those of a scanning electron microscope (SEM)?

Light microscopes use the light coming off of a specimen to produce a magnified image. SEM's emit electrons to amplify a signal that goes to a CC-TV and puts the specimen on a larger display

What are the advantages and some applications of an SEM?

SEM's produce higher magnifications, resolutions, and greater depth of focus. SEM's can be used to see the elemental composition of a specimen, to determine if a suspect recently fired a weapon, etc.

What are the different types of evidence associated with each type of microscope?

Compound: smaller objects (bullets, spores, etc)


Comparison: hairs, bullets, anything for side-by-side comparison


Stereoscopic: physical evidence that doesn't need high magnification


Polarizing: materials that polarize light (ex: soil)


Microspectrophotometer: trace evidence


SEM: evidence in need of extremely high magnification

What is the cuticle?

Scale structure covering hair exterior

What is the cortex?

Main body of the hair shaft

What is the medulla?

Cellular column running through the center of the hair

What are the three phases of hair growth?

Anagen: lasts up to 6 years, root attached to follicle, gives bulb flame-shape appearance


Catagen: lasts 2-3 weeks, roots look elongated, bulbs shrinks and is pushed out of follicle


Telogen: lasts 2-6 months, hair shed from follicle, root is club-shaped

What is the distinction between animal hair and human hair?

Human hairs rarely show a continuous medulla

What hair features are useful for comparison with other hairs?

1) Color


2) Length


3) Diameter


4) Absence or presence of medulla


5) Pigment distribution, shape, color intensity in cortex

What is the role of DNA typing in hair comparison?

DNA typing narrows down the possible suspects and exonerates others. It also provides a link between questioned hairs and reference hairs.

What are natural fibers?

Fibers derived from animal or plant sources

What are manufactured fibers?

Fibers derived from natural or synthetic polymers

Describe the structure of a polymer.

A polymer looks like a long, repeating chain, each link representing its basic structure. Thousands of links, called monomers, are linked to form a large chain

What properties of fibers are most useful for forensic comparison?

1) Color


2) Diameter


3) Lengthwise striations


4) Pitting

Describe proper collection and preservation of fiber evidence

1) ID and preserve potential "carriers" of fibers


2) Relevant articles placed in paper bag separately


3) Prevent articles from being in contact with different people or different locations


4) Carpets, rugs, bedding should be carefully folded to protect areas that may contain fibers


5) Car seats should be covered with polyethylene sheets to protect evidence


6) Knife blades should be covered to protect adhering fibers

Describe the components of paint

1) Pigment: provides color and opacity, sometimes other uses (ex: corrosion resistance)


2) Binder: binds ingredients together


3) Volatile vehicle: dissolves or disperses binder, allows coat to spread

Describe the proper collection and preservation of paint evidence

1) Paint chips must be picked up with papers or scooped with a piece of paper


2) Use druggist folds or put them in glass or plastic vials


3) If paint is smeared on an object or clothing, package the whole object carefully


4) Uncontaminated samples must be taken from an undamaged part of the vehicle in accident or hit-and-run situations


5) All layers of the sample must be taken down to the bare metal


6) Each sample should be packaged separately

What is psychological dependence?

Conditioned use of a drug causes by underlying emotional needs

What is physical dependence?

Need for a drug brought about by regular use (addiction)

Name and classify commonly abused drugs

1) Narcotics (morphine, opium heroin)


2) Hallucinogens (marijuana, LSD, PCP)


3) Depressants (alcohol, barbiturates, antipsychotics)


4) Stimulants (amphetamines, cocaine


5) Club drugs (ecstasy, Rohypnal, meth)


6) Anabolic steroids

Describe the tendency to develop psychological and physical dependency for the more commonly abused drugs

1) Narcotics: painkillers that depress blood pressure, heart rate, respiratory rate


2) Hallucinogens: induce changes in mood, attitude, thought process, perception


3) Depressant: depress functions of central nervous system


4) Stimulants: increase activity

Describe the schedules of CSA and how drugs are classified into each one

I: high abuse potential; no medical use; research only


II: high abuse potential; medical use only; no refills


III: less abuse potential; accepted medical use; refilled under authorization


IV: low abuse potential; medical use; refilled under authorization


V: must show low abuse potential; medical use; over the counter

Describe the lab tests that forensic chemists rely on to comprise a routine drug ID scheme

1) Color test: drugs yield certain color when in contact with certain chemicals


2) Microcrystalline test: ID substance by color and shape of crystals formed when substance is mixed with reagent


3) Chromatography: separates drugs from diluents


4) Mass spectrometry: separates drug from other substances present in prep


5) Spectrophotometry: absorption of UV and IR by drug can characterize drug

Describe proper collection and preservation of drug evidence

Properly package in original container and label with sufficient info

How is alcohol absorbed into the bloodstream?

Diffusion into the blood (more efficient in small intestine)

How is alcohol transported throughout the body?

Through the bloodstream to watery portions of the body (ex: brain)

How is alcohol eliminated?

1) Oxidation: alcohol converted to acetaldehyde and then acetic acid


2) Excretion: excreted out of breath, sweat, and urine

What are the important parts of the circulatory system?

Arteries: blood vessels carrying blood away from heart


Veins: vessels carrying blood to the heart


Capillaries: tiny vessels where materials are exchanged between blood and tissues

How is alcohol excreted from breath?

Alcohol in the blood is exchanged with fresh air in alveoli sacs and is discharged into the air

Describe the design of the Breathalyzer and names of the chemicals used to determine the presence of alcohol

The breathalyzer measures the absorption of light by potassium dichromate before and after its reaction with alcohol

How to calculate total magnification?

(objective magnification)(ocular magnification) ex: (4x-100x)(10x)

3 methods for DNA typing?

1) RFLP DNA typing


2) HLA DQ Alpha


3) STR analysis & multiplexing

What is the equation for blood spatter angle of impact?

sin^-1 {width/length}

What is the difference between plasma and serum?

Plasma is mainly water. Serum has antibodies.

What is the presumptive test for blood?

phenolphthalein test

What is the precipitin test?

When there is a precipitin line

How much alcohol is absorbed in the stomach and small intestine?

20% in the stomach


80% in the small intestine

How does alcohol get in urine?

If I doesn't go into the alveoli, it goes into the kidneys and then the urine

Explain the concept of infrared breath-testing devices.

In infrared devices, breath is blown into a chamber where an infrared beam is shone through. When it interacts with the alcohol, it decreases in intensity. This is measured and gives a signal proportionate to the concentration of alcohol in blood.

Beam of light

Explain the concept of fuel-cell breath-testing devices

A fuel (breath alcohol) and an oxidant (atmospheric oxygen) are converted into an electric current. As alcohol is converted into acetic acid, it generates a current proportional to the quantity of alcohol in the breath.

Fuel + oxidant = current

Describe common field sobriety tests.

1) horizontal gaze nystagmus


2) walk and turn


3) one-leg stand

List common lab procedures for measuring concentration of alcohol in the blood

1) gas chromatography


2) oxidation of alcohol to acetaldehyde

Describe precautions for preserving blood for analyzing its alcohol content

1) apply nonalcoholic disinfectant to area where blood is being drawn


2) preserved drawn blood put in airtight container after adding anticoagulant and preservative


3) container is stored in refrigerator

What is the impairment level in New York?

.08

Explain the significance of the implied consent law?

The implied consent law was passed to prevent a person from refusing to take intoxication tests

Describe techniques used to toxicologists to isolate and ID drugs and poisons

1) gas chromatography - sample separated into its components


2) thin-layer chromatography - uses liquid phase to separate mixture into components


3) immunoassay - based on specific drug antibody reactions


4) gas chromatography/mass spectrometry - sample separated into components and bombarded with high-energy electrons to produce spectrum that represents unique pattern

Describe roles of the Drug Recognition Expert and toxicologist

DRE - determines what and how much of a drug a suspect has taken

List the the A-B-O antigens and antibodies in each blood type

A: A, Anti-B


B: B, Anti-A


AB: AB, neither


O: neither, both

Define the roles of antibodies and antigens

Antibodies: destroys or inactivates specific antigens



Antigens: stimulates the body to produce antibodies against it

Why does agglutination occur?

It occurs because antibodies have two reactive sites, which can cause blood cells to clump together

How is whole blood typed?

By testing to see if the blood agglutinates when either anti-A or anti-B serum, both, or neither are present

What is the color test for bloodstains?

1) Color (phenolphthalein) test - when a bloodstain, reagent, and hydrogen peroxide are mixed, hemoglobin turns purple

What is the luminol test?

Reagent is sprayed in a darkened area and luminescence is used to determine bloodstains

Spray, blacklight

What is the precipitin test?

Determines if blood is animal or human; blood injected into an animal to form antibodies that react with invading human blood

What is the significance of the precipitin test to serology?

It only requires a small amount of blood and is capable of getting a positive reaction from blood that has been dried for extended periods of time

What is chromosome?

Rod-like structure in nucleus; composed of DNA and other proteins

What is a gene?

Unit of hereditary material

List the tests used to characterize seminal stains

1) Acid phosphatase test


2) microscopic examination


3) Prostate-specific antigen test

Describe collection of evidence related to a rape investigation

1) pubic area combed for foreign hairs


2) 15-20 full-length pubic hairs cut at skin line


3) external genital dry-skin area swabbed with one dry and one moist swab


4) 5 full-length head hairs cut at skin line from scalp


5) 20 mL of blood collected


6) undersurface of fingernails scraped over clean paper


7) all clothing carefully removed and packaged separately in paper bags


8) 30+ mL collected from victim to test for drugs related to rape

Describe location, distribution, and appearance of bloodstains and spatter patterns to to crime scene reconstruction

1) Direction from where blood originated


2) angle at which blood droplet struck a surface


3) location or position of victim when bloody wound was inflicted


4) movement of bleeding individual at crime scene


5) number blows struck to victim


6) approx. location of individual delivering blows that produced bloodstain pattern

What species of hair are found on the cuticle?

1) coronal - stacked cups


2) imbricate - dried skin


3) spinous - pineapple

What pairs are there for base pairing?

A=T


C=G

What are two amino acids?

Alanine: C-G-T


Aspartate: C-T-A