Evidence and Investigation: Forensic Science, Biology, Chemistry, Documents, and Pattern Evidence

Comprehensive vocabulary flashcards covering the core principles, techniques, classifications, and terminology of forensic investigation, evidence collection, document examination, toxicology, biology, and impression analysis.

Forensic Science

The application of science to law, characterized by neutral, impartial scientific analysis conducted to seek truth and link or eliminate suspects without working to bias an investigation.

Scientific Method (Investigations)

A five-stage investigative analytical cycle: observations leading to questions, questions generating hypotheses or theories, hypotheses tested through experimentation, experimental data analyzed, and hypotheses subsequently retested or re-evaluated.

Continuity of Evidence

The complete, unbroken accounting of all physical evidence from the crime scene to the courtroom, establishing controlled access, exact locations, and signed documentation for anyone who handles it.

Centre of Forensic Sciences (CFS)

The Ontario forensic laboratory system located in Toronto and Sault Ste. Marie that provides specialized scientific analysis in biology, chemistry, toxicology, documents, electronics, tool marks, and firearms for police, defence counsel, and civil proceedings.

Forensic Entomologist

A specialist who examines and identifies insect activity, such as fly larvae found on or near human remains, to assist investigators in estimating the elapsed time since death.

Forensic Pathologist

A medical specialist who conducts post-mortem examinations and autopsies to determine the official cause and manner of death.

Lay Witness

A courtroom witness who is restricted to testifying solely about firsthand factual observations of what they saw or heard, without being permitted to offer opinions.

Expert Witness

A witness possessing specialized training, education, and experience who did not view the incident firsthand but is formally qualified by a judge to interpret evidence and offer an expert opinion.

Class Characteristics

Physical or chemical properties of evidence that link an item to a general group or category while eliminating others, but cannot uniquely associate it with a single, individual source.

Individual Characteristics

Distinctive properties that link evidence to a single, unique source to the exclusion of all others, such as fingerprints, unique tool marks, dentition, or nuclear DNA.

DNA Typing

A forensic biology technique that utilizes an individual's unique genetic profile to identify a single donor, eliminate suspects, connect a repeat offender to multiple crimes, or identify deceased victims.

Nuclear DNA

Chromosomal genetic material located inside the cell nucleus that is unique to each individual (with the exception of identical twins) and serves as the primary standard for criminal casework identification.

Mitochondrial DNA

Genetic material situated within cellular mitochondria that is passed down strictly through the maternal line; it is shared among maternal relatives and is primarily utilized when remains are aged or degraded.

Presumptive Test

A rapid, inexpensive preliminary screening test conducted at a crime scene or laboratory to indicate whether a suspected stain is likely a specific bodily substance (such as blood).

Confirmatory Test

A comprehensive and definitive laboratory analysis that indisputably identifies the specific nature of a biological fluid or substance.

Luminol

A presumptive chemical spray reagent that detects latent or cleaned bloodstains by reacting with iron in hemoglobin to produce blue chemiluminescence visible in total darkness.

Bluestar

A latent bloodstain reagent applied at crime scenes that reveals latent blood without requiring absolute darkness and does not degrade or compromise subsequent DNA extraction.

Combined DNA Index System (CODIS)

An automated DNA databank system that indexes and cross-compares genetic profiles across offender, crime scene, victim elimination, and missing persons indexes.

Familial DNA

An investigative method that analyzes partial genetic matches in public genealogical or criminal DNA databases to identify potential suspects through close biological relatives.

Forensic Chemistry

The branch of forensic science dedicated to the identification and comparative analysis of non-biological trace evidence, including paint, glass, synthetic fibres, and explosive residue.

Forensic Toxicology

The branch of forensic science that identifies and quantifies poisons, illicit drugs, prescription medications, and alcohol inside biological matrices such as blood, urine, gastric contents, and tissue specimens.

Arson

The intentional and unlawful setting of a fire, investigated by the Office of the Fire Marshal (OFM) to examine burn origin points, char patterns, and chemical accelerant traces.

Accelerant

Any readily combustible substance, such as gasoline or lighter fluid, deliberately spread to initiate or rapidly spread a fire in an arson crime.

Primary Explosives

Supersensitive chemical explosive compounds that detonate rapidly and violently when subjected to minimal friction, heat, or impact shock (e.g., blasting caps).

Secondary Explosives

Relatively insensitive explosive formulations that require a strong shock wave from an initial primary detonation in order to detonate (e.g., dynamite, military explosives).

Clandestine Laboratories

Secret illicit drug manufacturing operations characterized by highly volatile, reactive, and toxic chemicals and improvised hardware that create extreme explosion and contamination risks.

Forensic Document

Any physical or electronic medium bearing symbols, text, handwriting, or markings conveying meaning to another party where authenticity, origin, or authorship is uncertain.

Exemplar (Handwriting)

A standard sample of known handwriting collected (naturally written prior to the crime) or requested (written under formal observation/warrant) to compare against a questioned document.

Natural Variation

The normal, inherent degree of deviation occurring naturally across instances of a person's handwriting, ensuring no single individual writes two words or signatures completely identically.

Disguised Handwriting

A deliberate effort by a writer to conceal their natural personal handwriting characteristics; because handwriting relies on semiconscious motor habits, disguised features usually revert after several paragraphs.

Latent Impressions (Document Examination)

Indented impressions transferred onto blank lower pages of a pad or notebook beneath where a written document was originally produced, recoverable through specialized oblique imaging or electrostatic detection.

Identification Officer

A forensic crime scene technician or police specialist trained in forensic photography, fingerprinting, evidence collection, casting, and continuity packaging for laboratory analysis.

Impression Evidence

Marks or indentations created when an object makes contact with another surface with sufficient force to transfer its shape, such as shoe prints, tire tracks, or tool bite marks.

Pattern Evidence

Observable structural arrangements and ridge designs present within an impression, such as fingerprint ridges, footwear tread designs, or tire tread layouts.

Patent Prints

Fingerprints that are readily visible to the unaided eye because the friction ridge skin made contact with a foreign transfer medium like wet paint, ink, dirt, or blood.

Latent Prints

Invisible friction ridge impressions transferred onto surfaces via natural skin oils or perspiration that require specialized chemical fuming or powder dusting to visualize.

Impression Prints (Fingerprints)

Three-dimensional friction ridge indentations left when a finger is pressed into a pliable, soft matrix such as fresh paint, mud, putty, or plasticine.

Three Groups of Fingerprints

The primary friction ridge pattern categories into which all fingerprints are grouped: Arches (plain or tented), Loops (radial or ulnar), and Whorls (double loop or accidental).

Fingerprint Comparison Conclusions

The three standard findings an identification specialist can conclude: insufficient detail to make an identification, exclusion (the prints originated from different individuals), or identification (both prints came from the same source).

Tire Impression Evidence

Three-dimensional tracks or two-dimensional residue impressions transferred from vehicle tires to a substrate, recorded through scaled photography and dental stone casting to match tread dimensions and unique wear characteristics.