Forensics Chapter 12 Recognition Of Bloodstain Patterns

Front 1

Discuss the (7) components of blood

Back 1

*Blood is pumped by the heart and circulates through arteries and veins carrying oxygen, nourishment, electrolytes, hormones, vitamins and antibodies to cells, while picking up carbon dioxide and other wastes.

*Blood is composed of a liquid portion called plasma that contains red blood cells, white blood cells, and platelets.

*Erythrocytes (RBCs) carry oxygen from the lungs to the cell of the body and return carbon dioxide to the lungs.

*Leukocytes (white blood cells) defend our bodies against infections and foreign substances.

*Platelets are the major components of clotting in our blood.

*When blood clots the fluid or liquid portion of the blood is called serum.

*The source of DNA in the blood comes from the nuclei of the white blood cells.

Front 2

What is surface tension? How does the surface tension of blood affect blood spatter?

Back 2

Surface tension is the force that pulls the surface molecules of a liquid toward its interior. This decreases the liquids surface area and causes the liquid to resist penetration. Blood surface tension is slightly less than water.

For blood splatter to occur the force exerted on the blood must be greater than blood’s surface tension. The shape of a drop of blood in the air is also affected by its surface tension. The shape of a drop of falling blood is spheroid.

Front 3

No matter how far a drop of blood falls it will not splatter (break into smaller droplets) unless something breaks its surface tension. What could break this surface tension?

Back 3

*The surface the drop strikes can break the surface tension. Hard, smooth, nonporous surfaces like tile or glass will create little splatter. Surfaces with a rough texture like wood or concrete can cause significant splatter. The protuberances extending from the rough surfaces break the surface tension causing splatter and parent stains with spiny (serrated edges).
Ex. p.214 figure 12.2

Front 4

What is spattered blood?

Back 4

Spattered blood is a random distribution of bloodstains with different sizes that may be produced in many different ways.
The size of spatter is affected by the amount of blood as well and the amount of force used. Spatter is created when enough force is used to overcome the surface tension of the blood.

Front 5

Identification and interpretation of spattered blood is...

Back 5

Identification and interpretation of spattered blood is important because it can be used to determine the location of the origin of the blood source, spatter on a suspects clothing puts them at the scene of the crime, and it may allow the determination of what mechanism (gun, knife, bat, etc) was used in the crime.

Front 6

How is Splatter affected?

Back 6

Splatter is affected not only by the amount of blood present and the force of the impact, but it is also affected by the texture of the surface the blood impacts.

Front 7

What is misting?

Back 7

Misting is generally associated with gunshots. Minute spatters of blood less than .1mm in diameter is considered misting. Misting is not generally seen.

Front 8

What is satellite spatter?

Back 8

Satelllite spatter is created by blood dripping into blood.

Front 9

Discuss impact spatter associated with beatings and stabbings.

Back 9

Impact spatter associated with beatings and stabbings usually has a size range 1 to 3mm in diameter. The force applied and the amount of available blood affects the size of the spatter.

Spatter can’t occur is there is no exposed blood, but the blood itself doesn’t have to be impacted. If a victim is bloody and it hit on another site of the body spatter can be produced.

The pattern of spatter is affected by the weapon used. Sharp objects (knives, glass, etc), blunt objects (bat, brick, etc), and the number of stabs or blows will all affect the spatter pattern. P. 219 figure 12.13

Front 10

What are castoff patterns?

Back 10

Castoff patterns are created with subsequent blows to the same general areas where a wound has occurred and blood has accumulated. Blood adhere to the object that produces the injuries. As an assailant swings the centrifugal force generated is enough to overcome the adhesive force of the blood and it is flung from the object forming a castoff pattern.

The blood that is flung will strike objects and surfaces like walls and ceilings.

Front 11

When is a projected bloodstain pattern produced?

Back 11

Projected bloodstain patterns are produced when the force exerted on the blood is greater than gravity. Vomiting blood is an example of projected blood. Running through a pool of blood can cause projected patterns as well.

Front 12

Discuss expirated bloodstain patterns

Back 12

Internal trauma can cause blood to accumulate in the lungs, sinuses, and airways of a victim. If the victim is living, blood will be expelled from the nose and mouth in order to free up the airways. The size and pattern of expirated blood are similar to impact patterns seen with beatings and gunshots.

Expirated bloodstain patterns can appear diluted if they are mixed with large enough quantities of saliva and mucus. Recently expelled blood will often have air bubbles mixed in because the blood has mixed with air in the lungs or air passageways. When the bubbles rupture and the blood dries the previous bubbles will appear as vacuoles. P. 222 figure 12.18

Front 13

What is a transfer pattern?

Back 13

A transfer pattern occurs when an object covered in blood comes into contact or is wiped on an unstained object or surface. The object that made the pattern can often be identified if a recognizable mirror image of the object is left on another object or surface.

Transfer patterns could be fingerprints, palm prints, footprints, hair, knives, or shoes. P. 223 figure 12.20 and 12.21

Front 14

How are diluted bloodstains often recognized?

Back 14

Diluted bloodstains (clean-up, rain, snow) are often impossible to recognize without the use of luminol treatments.

Luminol in a chemiluminescent reagent that is used as both as a presumptive test from blood as well as a method of chemicalenhancemnet of blood. Luminol is applied with a spraying technique and wide areas can efficiently be searched.

Luminol isn’t specific for just blood. Luminol will react with copprt, bleach, fecal matter, urine (containing small traces of blood), animal proteins, rust, and saliva.

Front 15

What are void areas or void patterns?

Back 15

Void areas or void patterns are absences of bloodstains in otherwise continuous patterns of staining. These patterns are usually seen when items have been removed from an area that was covered with blood spatter.

Front 16

What two questions arise when dealing with bloodstained clothing? +why?

Back 16

*Whose blood is on the clothing?
-DNA can be used to determine whose blood is on the clothing.

*How did the blood get into the clothing?
-Passive bloodstains: transfer, flow patterns, saturation, and dripping
-Active bloodstains: impact spatter, arterial bloodstains, expirated(like expired) bloodstains, castoffs, etc.

Front 17

The interpretation of bloodstain patterns on clothing often centers on what?

Back 17

The interpretation of bloodstain patterns on clothing often centers on substantiating or refuting a suspect’s version of how their cloths got blood on them.

Front 18

Could a suspect with no bloodstains on them be innocent of the crime? (why or why not?)

Back 18

Not necessarily!!! The absence of blood-staining could occur for the following reasons:
*The direction of the blows with a blunt object or stabs with a knife could have directed the blood spatter away from the suspect.
*The site of injury could have been covered with clothing or other material during the attack.
*The suspect could have cleaned up or changed cloths.
*The suspect could have worn protective outerwear.
*The suspect may have removed their clothing before the attack.
*The amount of blood at the crime scene could have occurred after the suspect left as the victim bled out.