TSA Forensic Science Preliminary Test

Forensic

relating to the application of scientific knowledge to legal questions

Observation

what a person perceives using his or her senses

Chain of custody

the documented and unbroken transfer of evidence

Circumstantial evidence

(indirect evidence) evidence used to imply a fact but not prove it directly

Class evidence

material that connects an individual or thing to a certain group (see individual evidence)

Crime-scene investigation

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

Crime-scene reconstruction

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

Datum point

A permanent, fixed point of reference used in mapping a crime scene

Direct evidence

evidence, that (if authentic) supports an alleged fact of a case

First responder

the first safety official to arrive at a crime scene

Individual evidence

a kind of evidence that identifies a particular person or thing

Paper bindle

a folded paper used to hold trace evidence

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

Some common examples of trace evidence include:

Pet hair on clothes or rugs

Hair on brushes

Fingerprints on a glass

Soil tracked into homes or buildings on shoes

A drop of blood on a T-shirt

A used facial tissue

Paint chips

Broken glass fragments

A fiber from clothing

Triangulation

a mathematical method of estimating positions of objects at a location such as a crime scene, given locations of stationary objects

Comparison microscope

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

Cortex

the region of a hair located outside the medulla that contains granules of pigment

Cuticle

the tough outer covering of a hair that is composed of overlapping scales

Gas chromatography

a method of separating chemicals to establish their quantities

Hair follicle

the actively growing base of a hair that contains DNA and living cells

Hair shaft

part of the hair above the follicle; contains mitochondrial DNA

Keratin

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

Medulla

the central core of a hair

melanin granules

particles of pigment found in the cortex of a hair

mitochondrial DNA (mtDNA)

genetic material in the mitochondria of the cytoplasm of a cell; only inherited from the mother

nuclear DNA

genetic material in the nucleus of a cell

Direct transfer

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

Fiber

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

Secondary transfer

the transfer of evidence such as a fiber from a source (for example, a carpet) to a person (suspect), and then to another person (victim)

Mineral fiber

a collection of mineral crystals formed into a recognizable pattern

Natural fiber

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

Synthetic fiber

a fiber made from a manufactured substance such as plastic

Arch

a fingerprint pattern in which the ridge pattern originates from one side of the print and continues to the other side

Core

the center of a loop

Delta

a triangular ridge pattern

Fingerprint

an impression left on any surface that consists of patterns made by the ridges on a finger

IAFIS (Integrated Automated Fingerprint Identification System)

FBI-developed national database of more than 76 million criminal fingerprints and criminal histories

Latent fingerprint

a concealed fingerprint made visible through the use of powders or forensic techniques

Loop

fingerprint pattern in which the ridge pattern flows inward and returns in the direction of the origin

Minutiae

the combination of details in the shapes and positions of ridges in fingerprints that makes each unique; also called ridge characteristics

Patent fingerprint

a visible fingerprint produced when fingers coated with blood, ink, or some other substance touch a surface and transfer their print to that surface

Ridge pattern

the recognizable pattern of the ridges found in the end pads of fingers that form lines on the surfaces of objects in a fingerprint. They fall into three categories: arches, loops, and whorls

Ten card

a form used to record and preserve a person's fingerprints

Whorl

a fingerprint pattern that resembles a bull's-eye

Ridge count

the number of ridges between the center of a delta and the core of a loop

Allele

an alternative form of a gene

Chromosome

nuclear cell structure that contains DNA in humans

Combined DNA Index System (CODIS)

the FBI's computerized criminal DNA databases as well as the software used to run these databases; includes the National DNA Index System (NDIS)

DNA fingerprint (profile)

pattern of DNA fragments obtained by analyzing a person's unique sequences of noncoding DNA

Electrophoresis

a method of separating molecules, such as DNA, according to size

Exon

portion of gene that is expressed

Segment

segment of DNA in a chromosome

Genome

all the DNA found in human cells

Intron

portion of a gene that is not expressed

Karyotype

picture of the paired homologous chromosomes and sex chromosomes in a cell

Polymerase chain reaction (PCR)

a method of amplifying (duplicating) minute amounts of DNA evidence for use in investigations

Primer

sequence of DNA added to trigger replication of a specific section of DNA

Restriction enzyme

" molecular scissors"; a molecule that cuts a DNA molecule at a specific base sequence

Restriction fragment

noncoding DNA fragment that restriction enzymes create, as in preparation for gel electrophoresis

short tandem repeat (STR)

sequence of repeating bases in noncoding regions of DNA that are used in DNA profiling

Agglutination

clumping of cells caused by an antigen—antibody response

Angle of impact

angle at which blood strikes a target surface relative to the horizontal plane of the target surface

Antibodies

proteins secreted by white blood cells that attach to specific antigens

Antigen

substance that provokes an immune response in the body

Antigen-antibody response

reaction in which antibodies attach to specific antigens; causes agglutination in cross blood-type transfusions

Area of convergence

two-dimensional view of the intersection of lines formed by drawing a line through the main axis of at least two drops of blood that indicates the general area of the source of the blood spatter

Area of origin

the location of a blood source viewed in three dimensions as determined by projecting angles of impact of individual bloodstains

Cast off pattern

blood projected onto a surface as a result of being flung from an object in motion

Passive drop

blood drop created solely as a result of gravity

Satellite drop

smaller droplets of blood projected from larger drops of blood upon impact with a surface

Spine

elongated blood streaks radiating away from the center of a bloodstain

Wipe

smeared blood pattern created when an object moves through blood that is not completely dried

Controlled substance

a drug or other chemical compound whose manufacture, distribution, possession, and use are regulated by the legal system

Depressant

a substance that decreases or inhibits the nervous system, reducing alertness

Hallucinogen

a drug that changes a person's perceptions and thinking during intoxication

Illegal drug

a drug that causes addiction, habituation, or a marked change in consciousness, has limited or no medical use, and is listed in Schedule I of the U.S. Controlled Substances Act

Narcotic

a n addictive, sleep-inducing drug, often derived from opium, that acts as a central nervous system depressant and suppresses pain

Poison

a natural or manufactured substance that can cause severe illness or death if ingested, inhaled, or absorbed through the skin

Stimulant

a substance affecting the nervous system by increasing alertness, attention, and energy, as well as elevating blood pressure, heart rate, and respiration

Tolerance

a condition occurring with consistent use of one drug whereby a person needs more and more of the drug to produce the same effect

Toxicity

the degree to which a substance is poisonous or can cause illness

Toxicology

the study of drugs, poisons, toxins, and other substances that harm a person when used for medical, recreational, or criminal purposes

Toxin

a substance naturally produced by a living thing that can cause illness or death in humans

algor mortis

cooling of the body after death

Autolysis

the breakdown of cells as they self-digest

Autopsy

medical examination to determine the cause of death

Cause of death

the injury or condition responsible for a person's death (such as heart attack, kidney failure)

Coroner

an elected official, either a layman or physician, who certifies deaths and can order additional investigations of suspicious deaths

Decomposition

the breakdown of once-living matter by living organisms

Livor mortis

the pooling of the blood in tissues after death that results in a red skin color

Manner of death

one of five ways in which a person's death is classified (i.e., natural, accidental, suicidal, homicidal, or undetermined)

Mechanism of death

the specific physiological, physical, or chemical event that stops life

Medical examiner

a physician who performs autopsies, determines the cause and manner of death, and oversees death investigations

putrefaction

destruction of soft tissue by bacteria that results in the release of waste gases and fluids

rigor mortis

the stiffening of the skeletal muscles after death

biological profile

estimation of the deceased's sex, age, stature, and ancestry, along with diseases and injuries, as derived from analysis of skeletal remains

diaphysis

the shaft of a bone

epiphysis

the unattached end of a bone that eventually becomes fused with the bone shaft

forensic anthropology

the use of skeletal anatomy to identify remains for legal purposes