Forensic Finals

Chromosomal DNA structure

A double helix of nucleotides bonded by A-T and C-G base pairs.

CODIS Acronym

Combined DNA Index System.

What is CODIS

A national database of DNA profiles used by law enforcement.

Gel Electrophoresis

A technique used to separate DNA fragments by size.

PCR

Polymerase Chain Reaction; a method to amplify small DNA samples.

STR

Short Tandem Repeat; repeating sequences of 2-6 base pairs used in DNA profiling.

VNTR

Variable Number Tandem Repeat; longer repeating DNA segments used in genetic profiling.

RFLP

Restriction Fragment Length Polymorphism; older DNA profiling method using fragment lengths.

What base pairing does A go to?

T (Thymine).

What base pairing does C go to?

G (Guanine).

Inheritance of mitochondrial DNA

Inherited from mom.

Inheritance of y-STRs

Inherited from dad.

Questioned document

A document whose authenticity is in doubt.

Blind forgery

Forgery made without seeing the original signature.

Simulated forgery

Forgery made by copying a genuine signature by sight.

Traced forgery

Forgery made by tracing an original signature.

Exemplar

A known sample of writing used for comparison.

Fraud

Deliberate deception for unlawful gain.

Where is microprinting located

Found in fine print on currency, checks, IDs.

Where is UV thread located

Embedded in currency and glows under UV light.

Where is color shifting ink located

Found on bills; changes color when tilted.

Ink analysis (chromatography)

Separates ink components for identification.

Voice print

Visual representation of voice/sound frequencies.

Area of convergence

Point where bloodstains originate when traced backward.

Point of Origin

The 3D location from which blood originated.

Angle of impact

The angle at which a blood droplet hits a surface.

Cast-off

Blood flung from an object in motion.

Swipe

Blood pattern from a moving object contacting a surface with blood.

Wipe

Blood pattern altered by a clean object moving through it.

Back spatter

Blood directed back toward the source of force.

Low velocity splatter

Large drops, typically from passive dripping.

Medium velocity splatter

Smaller drops, often from blunt force trauma.

High velocity splatter

Fine mist, often from gunshots.

Tail formation

Shows direction blood droplet traveled.

Scalloping

Wavy edge on blood stains indicating speed and direction.

Blood type

Classification based on presence of A, B antigens and Rh factor.

Antigens

Surface proteins on red blood cells determining blood type.

Secretor

A person whose antigens are found in body fluids.

Hemoglobin

Iron-containing protein in red blood cells carrying oxygen.

Kastle-Meyer blood test

Presumptive test that turns pink if blood is present.

Luminol blood test

Glows blue in dark when it reacts with blood.

Hemastix blood test

Strip test that changes color in presence of blood.

Precipitin blood test

Determines if blood is human.

Components of blood

Red blood cells, white blood cells, plasma, platelets.

B-cells

White blood cells producing antibodies.

T-cells

White blood cells involved in immune response.

Neurotransmitter

Chemical messenger in the nervous system.

Toxicity

Degree to which a substance is harmful.

LD50 (Lethal dose)

Dose that kills 50% of a test population.

Physical dependency

Body becomes reliant on a drug.

Psychological dependency

Emotional/mental craving for a drug.

Narcotic

Pain-relieving, often addictive drug (e.g. opioids).

Stimulant

Drug that increases brain activity (e.g. cocaine).

Depressant

Drug that decreases brain activity (e.g. alcohol).

Hallucinogen

Drug that alters perception/thought (e.g. LSD).

Controlled substance schedule I

High abuse, no accepted medical use (e.g. heroin).

Controlled substance schedule II

High abuse, limited medical use (e.g. morphine).

Controlled substance schedule III

Moderate abuse potential (e.g. ketamine).

Controlled substance schedule IV

Low abuse potential (e.g. Xanax).

Controlled substance schedule V

Lowest abuse potential (e.g. cough syrups).

Steroids

Drugs that mimic hormones; can enhance muscle growth.

Chromatography: thin layer

A flat-plate method for separating chemicals.

Chromatography: paper

Uses paper as a stationary phase.

Chromatography: gas

Separates gases or volatile substances.

BAC (Blood Alcohol Concentration)

Percentage of alcohol in a person's bloodstream.

Narcan (Naloxone)

Drug that reverses opioid overdose effects.

Latent print

Fingerprint not visible to the naked eye.

Plastic print

Fingerprint impressed into soft material.

Visible print

Fingerprint visible due to substance on finger (e.g. ink, blood).

AFIS

Automated Fingerprint Identification System.

Bifurcation

Where a single ridge splits into two ridges.

Ridge ending

Where a ridge suddenly ends.

Loop

Fingerprint pattern with one delta and a core.

Arch

Fingerprint pattern with no deltas; ridges enter and exit opposite sides.

Whorl

Fingerprint pattern with circular ridges and two deltas.

Level 1 fingerprint characteristic

General ridge flow and pattern.

Level 2 fingerprint characteristic

Minutiae like ridge endings and bifurcations.

Level 3 fingerprint characteristic

Pore shape, edge shapes, scars.

Superglue fuming

Cyanoacrylate fumes reveal latent prints.

Dusting

Powder applied to reveal fingerprints on nonporous surfaces.

Iodine fuming

Iodine vapor reacts with oils to visualize latent prints.

Compression

Tool leaves a mark by pressing into a surface.

Cutting

Produced by tools like wire cutters or scissors.

Sliding

Scratches left as a tool moves across a surface.