forensics midterm

GET ME OUT OF HERE!!!

Fact

A statement or information that can be verified.

Forensics

The application of science to resolve legal matters; derived from the Latin 'forensis' meaning 'of the forum.'

Eyewitness

A person who has seen someone or something related to a crime and can communicate their observations.

Opinion

Personal belief founded on judgment rather than on direct experience or knowledge.

Logic

Conclusions based on reason or facts.

Observation

What a person perceives using their senses.

Deductive Reasoning

Deriving a conclusion from the facts using a series of logical steps.

Perception

The brain's interpretation of sensory observations after filtering and processing information.

Brain Filtering

The process by which the brain fills in gaps in perception or ignores details to prevent sensory overload.

Paul Ekman (1967)

Discovered that humans make over 10,000 micro-facial expressions that are biologically programmed.

Micro-expressions

Rapid, involuntary facial expressions that reveal true emotions; 3,000 are relevant to emotion.

The Innocence Project

An organization that re-examines post-conviction cases using DNA to prove innocence.

70%

The percentage of wrongful convictions found by the Innocence Project to be caused by faulty eyewitness identification.

Forensic Scientist Goal

To find, examine, and evaluate evidence from a crime scene.

Forensic Scientist Skills

Must observe, interpret, and report; must be a good communicator to convince a jury.

Locard's Principle of Exchange

When a person comes in contact with an object or another person, a cross-transfer of physical material can occur.

Trace Evidence

Small but measurable amounts of physical or biological material found at a crime scene (hair, fibers, skin cells, etc.).

Direct Evidence

Firsthand observations such as eyewitness accounts, dashboard video cameras, or confessions.

Circumstantial Evidence

Indirect evidence used to imply a fact but not support it directly.

Class Evidence

Material that connects an individual or thing to a certain group (e.g., Blood type).

Individual Evidence

Evidence that identifies a specific person or thing (e.g., DNA or fingerprints).

Biological Evidence

Evidence derived from a living organism (blood, hair, saliva, DNA).

Physical Evidence

Non-living items such as glass, soil, fibers, or weapons.

First Responder

The first safety official to arrive at a scene; responsible for securing the area.

Primary Crime Scene

The actual location where the crime took place.

Secondary Crime Scene

A location related to the crime where evidence is found, but not where the crime occurred.

The 7 S's of CSI

Secure the scene, Separate the witnesses, Scan the scene, See the scene, Sketch the scene, Search for evidence, Secure and collect evidence.

Collusion

When witnesses work together to create a story (prevented by separating them).

Paper Bindle

A folded paper used to hold trace evidence securely.

Chain of Custody

The documented and unbroken transfer of evidence from crime scene to courtroom.

Evidence Log

A document attached to evidence containing case number, description, and names of collectors.

Crime-Scene Reconstruction

A hypothesis of the sequence of events from before the crime through its commission.

Hair Function

Primarily used by mammals for body temperature regulation (insulation).

Hair Follicle

The part of the hair under the skin that contains DNA (individual evidence).

Hair Shaft

The part of the hair above the skin made of keratin (class evidence).

Keratin

The fibrous protein that makes up the hair shaft.

Cuticle

The transparent outer layer of the hair shaft with scales pointing toward the tip.

Imbricate

The flattened, narrow scale pattern found in human cuticles.

Cortex

The inner layer of the hair shaft that contains melanin granules.

Melanin Granules

Pigment bits that give hair its color.

Medulla

The central lead-like core of the hair shaft.

Medullary Index

The ratio of the diameter of the medulla to the diameter of the entire hair.

Human Medullary Index

Typically 0.33 or less.

Animal Medullary Index

Typically 0.50 or higher.

Anagen Stage

The active growth stage of hair; lasts approximately 1,000 days.

Catagen Stage

The transitional stage where hair growth stops and the follicle recedes.

Telogen Stage

The dormant stage where the hair follicle is resting and hair is easily lost.

Dermis

The inner layer of skin where sweat glands and fingerprint ridges originate.

Dr. Nehemiah Grew (1684)

The first person to describe ridge skin in detail.

Loop

A fingerprint pattern where ridges enter and exit from the same side; has one delta (65% of people).

Whorl

A fingerprint pattern that resembles a bullseye; has two deltas (30% of people).

Arch

A fingerprint pattern where ridges enter one side and exit the other; has no deltas (5% of people).

Minutiae

Small ridge characteristics that make a fingerprint unique (bifurcation, dots, islands).

Bifurcation

A minutiae point where a ridge splits or forks into two.

Ending Ridge

A minutiae point where a ridge simply stops.

Enclosure (Island)

A minutiae point where a ridge splits and then quickly joins back together.

Patent Fingerprint

A visible print left on a smooth surface by a liquid (blood, ink, oil).

Plastic Fingerprint

A 3D indentation left in soft material like clay, putty, or wax.

Latent Fingerprint

A hidden print made visible only through the use of powders or chemicals.

Ninhydrin

A chemical used to recover latent prints from porous surfaces like paper.

Cyanoacrylate

Also known as 'Superglue fuming'; used to develop prints on non-porous surfaces.

Sir William Harvey (1628)

Noted that blood circulates continuously through the body.

Karl Landsteiner (1901)

Discovered the three blood types: A, B, and O.

Red Blood Cells

Cells that carry respiratory gases (Oxygen and Carbon Dioxide).

White Blood Cells

Cells that belong to the immune system and fight disease.

Platelets

Components of blood that aid in blood clotting and repair.

Type O Blood

The most common blood type (43% of the population).

Satellites

Small secondary drops of blood that separate from the main drop.

Spines

Elongated extensions of a blood drop that stay attached (caused by striking a porous surface).

Smooth Surface Spatter

Results in rounder blood stains with smooth edges.

Porous Surface Spatter

Results in irregular shapes with jagged edges and spines.

DNA Fingerprinting

A pattern of DNA fragments used to identify individuals.

Dr. Alec Jefferys (1982)

Developed techniques to examine highly variable regions of DNA for identification.

PCR (Polymerase Chain Reaction)

A lab technique used to make millions of copies of a DNA segment.

Electrophoresis

A method of separating DNA molecules based on their size.

STR (Short Tandem Repeats)

Repeating sequences of 2-6 DNA bases used to create a profile.