Fingerprints & Blood Forensics

The four parts of blood

Plasma, red blood cells, white blood cells, and platelets

Which part of the blood contains hemoglobin?

Red blood cells

If a person has B antigens what is their blood type?

B

If a person has no antigens what is their blood type?

O

If a person has anti-B antibodies what is their blood type?

A

A person with blood type AB can receive what blood types?

AB, A, B, O

Type B can be donated to which blood types?

AB, B

If Anti-A serum and Anti-B serum make blood clump, what type is it?

AB

If a blood sample does not clump with either type, what is it?

O

Which blood type is the most common in the US?

O

Likelihood equation

100/y x 100/y x 100/y

What are the roles of hemoglobin?

Carries oxygen, removes carbon dioxide, gives blood its red color

What do white blood cells do?

Fight of infection, attack bacteria viruses and other microbes. Crucial part of the immune system

What are three things that the body of a victim might be exposed to that can hinder finding prints on the skin?

Weather, decomposition, mutilation

What is one reason why a body should not be refrigerated before examining for latent prints?

Condensation on the skin can wash away prints

Ending ridge

line that stops

Fork

Two prongs coming off a ridge

Short ridge

Tiny line

Bridge

Connects the middle of two ridges

Hook

Curved line coming off the middle of a ridge

Plasma

Liquid portion of unclottted blood that contains proteins, involved in clotting

Serum

Liquid that remains after the clotting in a clump

Passive bleeding

Depends on gravity, oozes and drips

Projected bleeding

Force is applied other than gravity, arterial spurts, cast-off blood and impact spatter

Three pieces of information provided by bloodstain patterns

The origin of the bloodstains, types of instrument used, relative position of victim assailant and bystander

Impact angle

Slant at which the blood drops strike a surface

Directionality

The course the blood drop followed, determines convergence and origin

Point of convergence

2-D representation of the point where lines tracking the pathways of 2 or more spatters meet

Point of origin

3-D representation of the point where the lines tracking the pathways and angles of impact of 2 ore more spatters meet, indicates location of the blood source

Void pattern

An absence of blood spatters where you would expect to see them, often where the attacker stood

Impact spatters

Occur with beatings, stabbings, gun shots, when a foreign object impacts the victim

Projection spatters

Result from arterial bleeding, cast-off, and exhaled blood

Combination spatters

Includes impact and projection spatters together

Low velocity spatters

Occur when an objects moving less than 5ft/sec strikes a surface, creates large spatters

Medium velocity spatters

Come from objects moving between 5 and 100ft/sec, smaller spatters

High velocity spatters

When an objects strikes faster than 100ft/sec, very small spatter

Blowback

Entrance wound, the droplets travel in a direction opposite to the bullet’s direction

Forward spatter

Exit wound, the droplets follow the bullet’s direction

Transfer patterns

Object soaked in blood comes in contact with an unstained object

2 steps of reconstructing a crime scene from bloodstains

Investigators take control of the scene immediately, Investigators take photographs of the overall scene

What can makes fingerprints glow?

Luminol

Why is acid citrate added to donated blood?

To prevent clotting and preserve it for up to 42 days

Grooves

Narrow valleys in your fingerprints

Friction ridges

The hills in your fingerprints that make the pattern

Arches

Rise in the center, wavelike, 5%, plain or tented

Loops

One or more ridges that double back on each other, 60%, radial towards thumb, ulnar towards pinky

Whorls

Whirlpools, 35%, plain, central, double, accidental

Henry System

Fingerprint classification system where individual prints are assigned scores based on where whorls show up within a ten-finger set of prints

AFIS

Computer system thar scans and encodes fingerprints to store them in a massive database

Patent prints

Substance such as ink or grease is left behind as a visible print

Plastic prints

Impressed print into a soft surface such as wax or dust, 3-D

Latent prints

Invisible and need to be seen with special lighting or processing

Laser and ultraviolet

Used to cause the ridge pattern of fingerprints to glow so they can be photographed

Lifting prints

Laying transparent tape over the print, once peeled off the print pattern sticks to the tape and is put on a card for examination

Cyanoacrylate vapor

Heated or mixed with Sodium Hydroxide, releases vapors that bind to amino acids in print residue, white print

Iodine fuming

When heated, crystal iodine releases iodine vapors, iodine fumes combine with the oils in the print, brown print

Ninhydrin

Dipped in or sprayed, heated, purple-blue print

Silver Nitrate

Reacts with the Chloride (salt) in the print, forms Silver Chloride, under uv light it makes a black or reddish-brown print