Terminology Guide — printable binder packet — Bright Minds Forensic Science

Bright Minds Forensic Science · Course Pack

Terminology Guide — The Word Is the Claim

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Forensic vocabulary is not a pile of words to memorize — each term is a claim about certainty. A presumptive test can only suggest, never confirm; class characteristics narrow a group while individual characteristics point to a source. Getting the word right is getting the certainty right — and that is the whole discipline. Use “match” loosely and every result starts to sound like proof; the trained analyst has a graded vocabulary and says exactly what a comparison has earned.

The habit that scales

Keep a running vocabulary page at the back of the case notebook; add to it every time a new term of art appears, with a one-line note on exactly what it does and does not claim. When you hit an unfamiliar term, say the boundary out loud before you look it up — that retrieval is what fixes it in memory.

The core vocabulary

Term	Meaning	Where & what it tells you
Locard’s exchange principle	every contact leaves a trace	Crime scene. Two objects in contact exchange material, so a scene almost always holds transferable evidence.
chain of custody	the documented history of an item	Every unit. The unbroken record of who held the evidence and when — a single gap can make it inadmissible.
class characteristics	features shared by a group	Fingerprints, trace. Narrow the field to a category (a shoe size, a fiber type) but cannot point to one source.
individual characteristics	features unique to one source	Fingerprints, toolmarks. Fine details that can point to a single source — the basis for individualization.
individualization	linking evidence to one source	Fingerprints, DNA. The strong claim that evidence came from one source — reserved for the rare cases the features justify.
latent print	a print invisible to the eye	Fingerprints. Left by natural skin oils — must be developed with powder, chemicals, or an alternate-light source to be seen.
patent print	a visible print	Fingerprints. Left in a substance like ink or dust — visible without any development.
plastic print	an impression in a soft surface	Fingerprints. Pressed into a pliable material such as wax or putty, leaving a three-dimensional mark.
minutiae	the fine ridge details of a print	Fingerprints. Ridge endings and bifurcations compared point-by-point between a latent print and a known one.
presumptive test	a screening test	Blood, chemical analysis. Can only suggest what a substance is — a positive narrows possibilities but never confirms.
confirmatory test	a definitive test	Blood, DNA. Identifies a substance with high specificity — the step that supports a claim a presumptive test cannot.

Terminology Guide · continued

Core Vocabulary, Continued & Unit Clusters

Reference

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Term	Meaning	Where & what it tells you
trace evidence	tiny transferred material	Trace evidence. Hairs, fibers, glass, soil — small, easily missed, and usually class-level rather than individualizing.
chromatography	separating a mixture into parts	Chromatography & analysis. Pulls a mixture (ink, dye) apart into its components so their pattern can be compared.
Rf value	a component’s travel ratio	Chromatography. The distance a component moves divided by the distance the solvent front moves — a repeatable number for comparing samples.
blood typing (ABO)	sorting blood into groups	Blood & bodily fluids. Places a sample in a broad group — a class characteristic that can exclude, but cannot identify one person.
spatter / angle of impact	the shape and angle of a drop	Blood & bodily fluids. The geometry of a stain, read carefully, can suggest how and from where a drop traveled.
DNA profile / STR	a pattern of repeated DNA markers	DNA & biological. Short repeated sequences (STRs) that vary between people — the strongest biological comparison available.
match probability	how likely a random match is	DNA. A statistic, never proof — it states how rare a profile is, so a “match” is always a likelihood, not a certainty.
exclusion	ruling a source out	DNA, fingerprints. Often the most certain result available — the evidence definitively does not come from a given source.
striations / toolmarks	the fine scratch patterns a tool leaves	Ballistics & toolmarks. The marks a barrel or tool cuts into a surface, compared under a microscope to link — or exclude — a source.

High-value clusters by unit

Crime scenes & fingerprints — Locard’s exchange principle, chain of custody, class vs. individual characteristics, and the latent / patent / plastic print family. Scene processing and print comparison become a connected web.
Trace evidence & chemical analysis — trace evidence, chromatography, Rf value, and the presumptive vs. confirmatory distinction. Say exactly what a separated sample or a screening test does and does not establish.
Blood & bodily fluids — presumptive and confirmatory tests, blood typing (ABO), and spatter and angle of impact. Each marks how strong a claim the evidence supports.
DNA, ballistics & the courtroom — DNA profile / STR, match probability, exclusion, and striations and toolmarks. Each ties back to the same idea — a result is a likelihood the analyst reports, never a verdict.

How to actually use this

Don’t swallow the table in one sitting. Keep this page open during reading and lab; each time you meet an unfamiliar term, say what it claims — and what it does not claim — out loud before you check. The habit leaves your effort free for the part of forensic science that actually rewards it — judging what the evidence honestly supports.