IAI CSCSA flashcards

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

Locard's exchange principle

Every contact between two surfaces leaves a transfer of material in both directions. Investigators use it to link suspect, victim, and scene through trace evidence such as fibers, hairs, and soil.

Chain of custody

A chronological written record of each item's seizure, storage, and transfer, with signatures and dates. An unbroken record is required to show the evidence is the same item and unaltered.

Grid search pattern

A search in which parallel lines are walked in one direction, then repeated at right angles. The double pass reduces the chance of missing items in large outdoor scenes.

Spiral search pattern

A search that moves in widening circles from a central point outward, or inward toward the center. It suits small, contained scenes with a clear focal point.

Zone or quadrant search

The scene is divided into labeled sectors searched separately by assigned personnel. It suits large or irregular scenes such as buildings, fields, or multi-room structures.

Wheel or ray search

Searchers start at a central point and move outward along straight lines like spokes. It is used for small scenes with a concentrated center of evidence.

Strip or line search

Searchers walk parallel lanes across the scene, each covering a narrow strip. It is fast and suited to large open areas but can miss items between lanes.

Overall photograph

A wide image showing the entire scene and its surroundings, establishing layout and context. It is taken before closer views and before any item is moved.

Mid-range photograph

A photograph showing an item with enough surrounding area to establish its position relative to fixed features. It bridges the overall view and the close-up detail.

Evidence scale placement

The scale is placed in the same plane as the item and adjacent to it, not tilted or above. This keeps size and shape measurable from the photograph.

Rough sketch requirements

A field sketch records fixed reference points, right-angle measurements, item numbers, a north arrow, and a legend. It later supports a scale drawing without returning to the scene.

Paper packaging for biologicals

Biological items are air-dried and placed in paper containers so moisture escapes. Plastic traps humidity, promotes mold and bacterial growth, and degrades DNA.

Perimeter and inner cordon

An outer boundary limits access and an inner boundary protects the focal area. Only essential personnel cross the inner cordon, and a log records every entry.

Scene control log

A written record of everyone who enters or leaves the scene, with name, agency, time, and purpose. It supports contamination defense and reconstructs who handled what.

Point of entry documentation

The entry point is examined for tool marks, trace, and footwear impressions on both faces. It marks where the offender entered and likely left transfer evidence.

Livor mortis

Postmortem settling of blood produces dependent lividity that fixes after several hours. Its pattern can indicate whether a body was moved after death, informing scene reconstruction.

Rigor mortis

Postmortem stiffening of muscles begins in small muscles and progresses, then resolves. Its stage is a rough, temperature-dependent indicator of time since death.

Coroner versus medical examiner

A coroner is usually an elected official with varied qualifications; a medical examiner is typically an appointed physician, often a pathologist. Jurisdiction and legal authority vary by system.

Manner of death categories

Deaths are classified as natural, accident, suicide, homicide, or undetermined. Manner differs from cause, which is the specific injury or disease process that ended life.

Footwear impression casting

A cast preserves three-dimensional impressions in soil or snow. Photograph first, then cast, and package the cast so the impression surface is not contacted or broken.

Latent print development sequence

Porous surfaces use powders, ninhydrin, or physical developer; nonporous surfaces use cyanoacrylate fuming, powders, or vacuum metal deposition. Sequence matters because some treatments preclude others.

Alternate light source use

Ultraviolet and blue light can reveal biological fluids, hairs, and treated prints not visible in normal light. Document findings and photograph with appropriate filters before collection.

Reference DNA sample

A known sample from a victim, suspect, or elimination person used to compare against scene profiles. Elimination samples are essential to separate investigator or victim DNA from offender DNA.

Substrate control

A sample of unstained material adjacent to a stain, collected to test for background DNA or interfering substances. It strengthens interpretation of the evidentiary sample.

Swabbing technique for DNA

Use a sterile swab moistened with the appropriate solution, concentrate the stain, air-dry, and package separately. Avoid oversaturating and change swabs between areas to prevent mixing.

Questioned versus known sample

A questioned sample is the item of unknown origin from the scene; the known sample is from a known source. Comparison requires both to be collected and preserved under comparable conditions.

Crime scene reconstruction

A reasoned account of events built from scene documentation, evidence positions, injury patterns, and physical testing. It is tested against alternative hypotheses rather than assumed.

Staged scene indicators

Signs include wounds inconsistent with the account, valuables left untouched, and evidence that does not fit the narrative. Investigators test the stated account against physical findings.

Vehicle scene preservation

Photograph the vehicle in place before moving, note positions of doors, gears, and lights, and protect trace evidence in the interior. Vehicle position and configuration can indicate sequence of events.

Fire scene origin determination

Investigators examine burn patterns, char depth, and low burning for origin. Accelerant samples are collected in clean metal cans with controls from unaffected areas.

Digital evidence at scene

Photograph device state and screen, note power and network status, and avoid altering data. Preserving volatile data and documenting the device as found protects authenticity.

Scene documentation priority

Document the scene as found before collection, and collect before removal only after photographs, sketches, and notes. Altering the scene first destroys positional context and reconstruction value.