Forensics Unit 1-5 Test Review

What types of cells are present in blood?

Red, White, Platelets, and Plasma

What type of evidence is blood typing?

Class Evidence

What are the possible genotypes of blood?

AA, AO, BB, BO, AB, OO

What are the possible phenotypes of blood?

A blood, A blood, B blood, B blood, AB blood, O blood

What is the US population breakdown of blood phenotypes?

Type O: 43%
Type A: 42%
Type B: 12%
Type AB: 3%

What is the Rh factor?

Another red blood cell protein is found on the surface of the red blood cell.

What is the US population breakdown of Rh?

85% Rh+
15% Rh-

What are antigens?

A molecule that induces an immune response

What are Antibodies?

Y-shaped immune system that detects and neutralizes pathogens

What is agglutination?

Blood clumping when 2 different blood types come in contact.

Describe the process of testing blood types.

Blood is mixed with A antibodies, B antibodies, and Rh antibodies. A blood clumps with anti-A, and B blood clumps with anti-b. AB clumps with both Anti-A and B. O clumps with neither. Rh+ clumps with anti-Rh and Rh- does not. O- is the universal donor. AB+ is the universal acceptor.

What is the purpose of luminol? How does it work?

Powder mixed with hydrogen peroxide. The iron in the blood speeds up the reaction between luminol and H202, which creates a blush glowing light when it reacts to blood.

What are the two tests that confirm a sample is blood?

Kastle-Meyer and Leukomalachite Green tests.

What test confirms that blood is human?

Elisa Test

What can be predicted based on blood spatter evidence?

It can determine the potential events of the crime as well as where someone was.

Describe the properties of blood.

Viscosity- thicker/more dense than water
Adhesion- sticks to other things
Cohesion- sticks to itself
Surface Tension- forms drop
Clots- thickens into almost a gel

What affects blood spatter evidence?

Surface- smooth VS. rough/porous surface will change the shape of a blood drop. A smooth surface is circular and rough/porous surfaces have spines and satellites.
Height- The height from which blood falls affects size and shape.

What types of injuries can blood spatter evidence explain?

Sharp force, blunt force, and gunshot injuries.

Describe how each blood spatter injuries look.

Sharp Force- Made with sharp, small surface area objects(knife, ice pick, etc). Less blood is transferred to objects leading to mainly linear stains.
Blunt Force- Made with large surface area objects(hammer, bat, etc). More blood is transferred to objects leading to drops of varying sizes.

Why is the angle of impact critical?

Changes in the elongation can be used to determine the area of convergence(2D) and point of origin(3D).

Why is the area of convergence important?

So you can see what direction the blood came from.

What are the three basic types of bloodstains?

Passive Stains, Transfer Stains, and Impact Stains.

What are the basics of blood spatter patterns?

Basic fall, arterial spurts of gushes, splashes, smears, trails, and pools.

deductive reasoning

Deriving consequences from facts using a series of logical steps

direct evidence

Directly proves a fact or is a firsthand observation; example: eyewitness

circumstantial evidence

Indirect proof that can be used to imply a fact but not directly prove it; example: fingerprints

physical evidence

Evidence derived from non-living sources; example: bullet casings

biological evidence

Evidence derived from living sources; example: hair

class evidence

Evidence with characteristics that belong to a group rather than a single source; example: type of car

individual evidence

Evidence with characteristics that belong to a single source at the exclusion of all other sources; example: DNA

CSI

crime scene investigation (or investigators)

inadmissible

Not accepted as evidence in court

admissible

accepted as evidence in court

First responder's role

Police officer secures the scene to prevent loss or damage of evidence

Crime scene investigator's role

Documents crime scene; searches for evidence, photographs evidence and collects evidence

Medical examiner/ coroner's role

Identifies body, observes the crime scene and state of the body, collects the body and brings it to the lab for the autopsy

detective’s role

Looks for leads, interview witnesses, works collaboratively with CSI

chain of custody

The chronological paper trail that records the sequence of custody, control, transfer, analysis, and disposition of evidence

Securing the scene (barricade the scene and restrict entrance to the scene)

1st step

Separating the witnesses

2nd step

Scanning the scene (identifying evidence)

3rd step

Seeing the scene (photographing the scene)

4th step

Sketching the scene

5th step

Searching the scene

6th step

Securing and collecting evidence

7th step

5th amendment

Right to remain silent, right to due process (fair trial), right to no double jeopardy (person can't be tried again after being acquitted)

6th amendment

Right to a lawyer and a speedy, public trial with impartial jury

fyre standard

To be admissible in court scientific techniques must be generally accepted by the scientific community; more strict guidelines

daubert ruling

Increased flexibility to the admissibility of scientific evidence; up to the judges if scientific evidence can be presented in court

how are small items stored

paper bindle

how are wet items stored

Dried and placed in breathable packaging to prevent molding

how are items that contain accelerants stored

Mason jar or similar container to prevent vapors from escaping

direct evidence

testimony

circumstantial evidence

evidence that relies on an inference to connect it to a conclusion of fact, such as a fingerprint at the scene of a crime

physical evidence

any tangible evidence

biological evidence

blood, saliva, hair, bone, tissue (from living organism)

trace evidence

tiny microscopic material (hair, fiber, glass, paint) (locard exchange principle)

class

non-specific, common

individual

linked to single source/person

linear search pattern

fastest, large open areas, many people

spiral search pattern

fast, one object of interest, few people, can miss evidence

grid search pattern

twice as long as linear search, thorough

quadrant/zone search pattern

most deliberate and slow, breaks up multiple zones, for large scenes, most effective, allows multiple people to work simultaneously

Fbi

fingerprint, blood sample, fibers, shoe impression, handwriting, paint transfer, DNA sample

IAFIS

fingerprint

FDDU

DNA sample

NHTSA

vehicle identification

ATF

bullet casing

transfer evidence

locard principle, contact between persons and objects or persons and persons

transient evidence

temporary, easily changed or lost, usually observed by first officer at scene. odor, temp, footprints

pattern evidence

produced by direct contact between a person and object or 2 objects, blood, gunpowder residue, footprints

associative evidence

something that may associate a victim/suspect with scene or each other. personal belongings

four aspects or crime scene investigation

recognition, identification, individualization, reconstruction

basic rules for packaging

dry- plastic bag, biological- bindle, liquid- unbreakable airtight container

chemical evidence

fibers, glass, gunpowder plastic, paint, cosmetic

testimonial

under oath satement (direct evidence)

questions answered by physical evidence

nature of offense and situation it was observed, characteristic of witness, manner in which info is retrieved

natural

comes from animals or plants such as wool or cotton

synthetic

comes from man made materials such as nylon, polyester, acrylic

direct transfer

the passing of evidence directly from a source to the victim or crime scene, which creates a direct link between them

non destructive

different ways fibers are tested- polarizing light microscopy and infrared spectroscopy

destructive

different ways fibers are tested- burning, solvents, staining, density, chromatography

synthetic fiber

manmade fiber created through chemical processes. made from polymers which are a long string of repeating chemical units called monomers

secondary transfer

the process where evidence is moved from a person to an object indirectly through another object first

fiber weave patterns

plain, twill, satin

nondestructive techniques for analyzing fibers

non destructive- polarizing light microscopy and infrared spectrocopy

examples of natural fibers

cotton, wool, cashmere, angora, silk, coir, asbestos

patent fingerprint

fingerprints left from ink, blood, paint, or another fluid on a surface that's visible to the eye

methods for analyzing latent fingerprints

chemical reaction or dusting with powders and lifted with clear tape

minutiae

details of a fingerprint that serve as unique characteristics, such as where a ridge ends or splits

plastic fingerprint

actual indentations left in some soft material such as clay, putty, or wax

automated fingerprint identification system

what is afis

loop and whorl patterns but not arch patterns

a core is present in what fingerprints

60% loops, 35% whorls, 5% arches

what are the percentages of likelihood for each type of fingerprint

individual

fingerprints are what type of characteristics

no, they stay the same from before birth

do fingerprint patterns change as you get older

they can trace it back to the individual

what information can investigators get from fingerprints

hair follicle

the actively growing, living part of the hair embedded in the skin that contains nuclear DNA

cuticle

outermost layer, face up

cortex

contains pigments