IAI CSSA flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

Locard's exchange principle

States that contact between two objects results in mutual transfer of material. Investigators use it to infer links between suspect, victim, and scene, and to justify trace evidence collection.

Chain of custody

Chronological written record of every person who handled or transferred an item of evidence, with dates, times, and purposes. Unbroken documentation supports authenticity and admissibility in court.

Primary crime scene

The location where the criminal act actually occurred. It is distinguished from secondary scenes, which are other places where evidence or consequences of the crime are found.

Secondary crime scene

Any location other than the original site where evidence related to the offense is discovered, such as a vehicle, dump site, or suspect's residence. Each requires its own documentation.

Grid search pattern

A search method in which the area is walked in parallel lines, then searched again along lines perpendicular to the first pass. It is slower but suits high-value, high-thoroughness outdoor scenes.

Strip or line search

Searchers move in parallel straight lines across an area, often spaced arm's length apart. It suits large open outdoor scenes with many personnel and low ground cover.

Zone or quadrant search

The scene is divided into labeled sections, each assigned to a searcher or team. It suits irregular, cluttered, or multi-room scenes where a single pattern cannot be maintained.

Spiral search pattern

A single searcher moves in expanding or contracting circles from a central point or inward from the perimeter. It suits confined or circular areas and small teams.

Rough sketch

A hand-drawn, not-to-scale diagram made at the scene showing item locations, fixed reference points, and measurements. It later supports the finished scale drawing.

Triangulation measurement

Locating an item by measuring from two fixed reference points to the item, forming a triangle. It fixes position without relying on a single baseline.

Baseline measurement

A measuring method using a straight reference line between two fixed points, with items located by perpendicular distance from that line and distance along it.

Overall photograph

A wide image showing the entire scene in context, including entrances and surroundings. It establishes where later mid-range and close-up images were taken.

Scale in evidence photography

A ruled or labeled reference object placed beside the evidence in close-up images. It allows viewers to judge true size and supports later measurement.

Scene perimeter control

Establishing an outer boundary, entry log, and access restriction so that only authorized personnel enter. It prevents contamination and preserves original scene conditions.

First responder scene duties

Render medical aid, secure and isolate the scene, detain witnesses and suspects present, and record original conditions such as lights, doors, and weather before anything is altered.

Scene release

Formal handover of the scene after documentation and collection are complete, recorded in writing with the time and receiving authority. It ends investigator control of the location.

Contamination avoidance

Using gloves, changing them between items, avoiding eating or smoking at scene, and packaging items separately. It prevents transfer that could undermine evidentiary value.

Reference sample

A known sample taken for comparison, such as a suspect's buccal swab, fingerprints, or known handwriting. It is compared against questioned evidence samples.

Questioned sample

Evidence of unknown origin collected at the scene, such as a stain or print, that will be compared against a known reference sample.

Evidence packaging rule

Biological and damp items are packaged in breathable containers and dried; sharp items are secured in rigid containers; each item is separately packaged and labeled.

Macroscene versus microscene

Macroscene is the visible scene and its surroundings; microscene is the trace-level evidence within it. The distinction concerns scale, not relative importance.

Walkthrough

An initial slow survey of the scene by the lead investigator before collection begins, used to plan search patterns, photography sequence, and evidence priorities.

Scene entry log

A written record of every person entering and leaving the scene, with name, agency, purpose, and time. It supports contamination defense and reconstructs scene history.

Cross-contamination

Transfer of material between evidence items, persons, or locations via tools, gloves, or footwear. Separate packaging and tool cleaning are the standard countermeasures.

Alternate light source

A filtered lamp producing specific wavelengths, used to reveal latent biological fluids, fibers, or treated surfaces not visible under normal lighting. Findings are documented before enhancement.

Control sample at scene

An unstained or unaffected sample taken near evidence, such as adjacent substrate or carpet. It establishes background composition when interpreting test results.

Search pattern selection

Choice of line, grid, zone, or spiral depends on terrain, scene size, personnel available, and required thoroughness. The chosen pattern is recorded in scene notes.

Fixed reference point

A permanent feature such as a wall corner or utility fixture used for measurements and repeated photographs. It allows later reconstruction of item positions.

Evidence item numbering

Each collected item receives a unique identifier cross-referenced in photographs, sketches, and the evidence log. Consistent numbering links documentation to the physical item.

Scene security alteration note

A written record of any change made for safety or medical reasons, such as a moved body or opened door, with time and reason. It protects later reconstruction.

Buccal swab

A reference DNA sample collected by swabbing the inside of the cheek. It provides known genetic material for comparison with questioned biological evidence.

Latent evidence

Evidence not visible to the unaided eye, such as fingerprints, biological fluids, or trace fibers. It requires specific detection techniques and documentation before enhancement.

Scene documentation triad

The combination of notes, photographs, and sketches that together record scene conditions and evidence locations. Courts expect all three to corroborate one another.