Common Terms

A full glossary of crime scene investigation terms maintained by the National Institute of Justice is available online.

Alternate light source - Special lighting device that produces visible and invisible light at various wavelengths to help investigators locate and visually enhance items of evidence (e.g., fluids, fingerprints, clothing fibers).

Associative evidence - any evidence that can link a person or an item to the scene of the crime.

Biological evidence - physical evidence such as bodily fluids that originated from a human, plant or animal.

Chain of custody - The process used to maintain and document the chronological history of the evidence. Documents record the individual who collects the evidence and each person or agency that subsequently takes custody of it. This chain of custody verifies that the evidence being analyzed is the same evidence found at the scene and helps ensure there was no opportunity for the evidence to be tampered with.

Contamination - The unwanted transfer of material from another source to a piece of physical evidence. The inadvertent touching of a weapon, thereby adding fingerprints to it is an example of evidence contamination.

Control sample - material of a known source that presumably was uncontaminated during the commission of the crime.

Cross-contamination - The unwanted transfer of material between two or more sources of physical evidence. For example, improperly collecting biological evidence such as blood could lead to one sample mixing with another sample and contaminating both.

Elimination sample - material of a known source taken from a person who had lawful access to the scene.

First responders - The initial responding law enforcement officer(s) and/or other public safety official(s) or service provider(s) arriving at the scene prior to the arrival of the investigator(s) in charge.

Fluorescent powders - Powder containing fluorescent chemicals that is applied to a surface to reveal latent prints; used in conjunction with an alternate light source.

Impression evidence - Objects or materials that have retained the characteristics of other objects that have been physically pressed against them.

Latent print - A fingerprint, palm print or footprint that is not readily visible under normal lighting.

Locard’s Exchange Principle - the theory that every person who enters or exits an area will deposit or remove physical material from the scene.

Other responders - Individuals who are involved in an aspect of the crime scene, such as perimeter security, traffic control, media management, scene processing, and technical support, as well as prosecutors, medical personnel, medical examiners, coroners, forensic examiners, evidence technicians, and fire and rescue officers.

Presumptive test - a test that is typically conducted at a crime scene that provides investigators with basic information regarding the compound in question. Presumptive tests can typically reveal the class of evidence, but are unable to confirm the specific compounds of which it is comprised.

Probative - possessing the potential to provide details that are valuable to an investigation.

Reconstructive evidence - reconstructive evidence allows investigators to gain an understanding of the actions that took place at the scene; a broken window, a blood spatter pattern, bullet paths and shoe prints.

Reference sample - material from a verifiable/documented source which, when compared with evidence of an unknown source, shows an association or linkage between an offender, crime scene, and/or victim.

Trace evidence - Physical evidence that results from the transfer of small quantities of materials (e.g., hair, textile fibers, paint chips, glass fragments, gunshot residue particles).

Transient evidence - Evidence which by its very nature or the conditions at the scene will lose its evidentiary value if not preserved and protected (e.g., blood in the rain).

Unknown/questioned sample - evidence of unknown origin; these samples could be found at a crime scene, transferred to an offender during commission of a crime, or recovered from more than one crime scene.

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