Forensic Science and Observation Skills Practice Flashcards

Vocabulary flashcards covering the fundamentals of observation skills, crime-scene investigation, hair analysis, and fiber examination based on forensic science lecture material.

Analytical skills

The ability to identify a concept or problem, to isolate its component parts, to organize information for decision making, to establish criteria for evaluation, and to draw appropriate conclusions.

Deductive reasoning

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

Eyewitness

A person who has seen someone or something and can communicate these facts.

Fact

A statement or assertion of information that can be verified.

Forensic

Relating to the application of scientific knowledge to legal questions.

Logical

Conclusions drawn from assumptions and known facts.

Observation

What a person perceives using his or her senses.

Opinion

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

Perception

Interpreting information received from the senses.

The Innocence Project

An organization created by Barry C. Scheck and Peter J. Neufeld in 1992 to reexamine post-conviction cases using DNA evidence to provide conclusive proof of guilt or innocence.

Paul Ekman

A leading expert on facial analysis and deception who discovered that facial expressions are universally understood and biologically programmed.

Microexpressions

Rapid changes in expression that last only a fraction of a second but reveal a person’s true feelings.

Chain of custody

The documented and unbroken transfer of evidence.

Circumstantial evidence

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

Class evidence

Material that connects an individual or thing to a certain group.

Individual evidence

A kind of evidence that identifies a particular person or thing.

Crime-scene investigation

A multidisciplinary approach in which scientific and legal professionals work together to solve a crime.

Crime-scene reconstruction

Forming a hypothesis of the sequence of events from before the crime was committed through its commission.

Direct evidence

Evidence that (if true) proves an alleged fact, such as an eyewitness account of a crime or a confession.

First responder

The first police officer to arrive at a crime scene.

Paper bindle

A folded paper used to hold trace evidence; also known as a druggist’s fold.

Primary crime scene

The location where the crime took place.

Secondary crime scene

A location other than the primary crime scene, but that is in some way related to the crime, where evidence is found.

Trace evidence

Small but measurable amounts of physical or biological material found at a crime scene, such as hair, skin cells, or clothing fibers.

Locard’s exchange principle

States that when a person comes into contact with an object or another person, a cross-transfer of physical evidence can occur.

Comparison microscope

A compound microscope that allows the side-by-side comparison of samples, such as of hair or fibers.

Cortex

The region of a hair located outside of the medulla containing granules of pigment.

Cuticle

The transparent, tough outer covering of a hair shaft composed of overlapping scales.

Hair follicle

The actively growing root or base of a hair containing DNA and living cells.

Medulla

The central core of a hair fiber.

Keratin

A type of fibrous protein that makes up the majority of the cortex of a hair.

Melanin granules

Bits of pigment found in the cortex of a hair that give hair its color.

Medullary index

The ratio of the diameter of the medulla to the diameter of the entire hair; humans typically have an index of $0.33$ or less, while animals have an index of $0.5$ or more.

Neutron activation analysis (NAA)

A method of analysis that determines composition of elements in a sample, capable of identifying up to 14 different elements in a single 2-cm strand of hair.

Anagen stage

The period of active growth when the cells around the follicle are rapidly dividing, lasting approximately 1,000 days.

Catagen stage

The transition stage of hair growth where the hair grows and changes, accounting for about 2 percent of all hair growth.

Telogen stage

The final stage of the hair cycle where the hair follicle is dormant or resting and hairs are easily lost.

Fiber

The smallest indivisible unit of a textile, it must be at least 100 times longer than wide.

Textile

A flexible, flat material made by interlacing yarns (or “threads”).

Yarn

Fibers that have been spun together.

Direct transfer

The passing of evidence, such as a fiber, from victim to suspect or vice versa.

Secondary transfer

The transfer of evidence such as a fiber from a source to a person (suspect), and then to another person (victim).

Natural fiber

A fiber produced naturally and harvested from animal, plant, or mineral sources.

Synthetic fiber

A fiber made from a man-made substance such as plastic.

Monomer

A small molecule that may bond to other monomers to become a polymer.

Polymer

A substance composed of long chains of repeating units.

Amorphous

Fibers without a defined shape; composed of a loose arrangement of polymers that are soft, elastic, and absorbing.

Crystalline

Regularly shaped fibers composed of polymers packed side by side, which make it stiff and strong.

Mineral fiber

A collection of mineral crystals formed into a recognizable pattern.