Forensic Blood Analysis

Plasma, red blood cells, white blood cells (have dna), platelets

What are the four main components of blood and which would allow you to individualize a suspect?

Antigen

a molecule found on the surface of blood cells

Antibody

a protein secreted by the immune system

that reacts with foreign substances

A antigens and D (Rh) antigens

A person with A+ blood would have which type of antigens on their cells?

No

Is it possible for a mom who is type O and a father who is type AB blood to have a type O child?

Kastle-Meyer Test: solution turns purple in presence of blood and Luminol: if blood is present will glow when sprayed

List two ways in which you can test a stain to confirm that it is in fact blood.

Precipitin test

Once you have confirmed something is blood, how can you confirm that it is human blood?

Antigen-antibody test: add a drop of blood and a drop of each anti-serum to the wells and look for clumping

Once you confirm something is human blood, describe how you would type the blood.

Origin of blood, Where the people were standing, Number of times a victim was struck, Type of weapon used

In crime scene investigations, what information can blood pattern analysis tell you?

Passive Blood Spatter

force of gravity alone ex. drops, drip patterns, flow patterns, pools

Blood Transfer

contact between a wet, blood-bearing surface and a surface that may or may not have blood on it ex. contact, swipe, wipe

Projected Blood Spatter

force greater than gravity applied to create pattern ex. arterial spurt, cast-off, back-spatter, expiratory, impact

faster = larger

How does speed affect blood drop size and shape

higher = larger

How does height affect blood drop size and shape

smooth = little to no distortion, rough = distorted (lots of spikes and spines)

How does surface type affect blood drop size and shape

Small drops of blood that are distributed around the original drops, can indicate direction of travel

What is satellite spatter?

tail of drops point in the direction of travel And secondary drops come off the parent in the direction of travel

When looking at a blood drop on a surface, specifically what 2 factors can help determine the direction the blood was travelling?