IAI CSSA key terms

The idea that whenever two objects come into contact, material is transferred from one to the other. It underpins the search for trace evidence and the argument that a suspect leaves something behind and takes something away.

Small quantities of material such as hair, fibers, glass, paint, soil, or gunshot residue transferred during contact. It is often invisible to the eye and requires special collection and laboratory analysis.

The chronological written record of who handled an item of evidence, when, and for what purpose. Gaps or undocumented transfers can undermine its admissibility and evidentiary weight in court.

The first officer or emergency personnel to arrive at a scene. Their priorities are safety, medical aid, securing and preserving the scene, and documenting initial conditions before anything is moved.

Controlling access to the scene using barriers, guards, and an entry point so that unauthorized persons cannot enter, contaminate evidence, or disturb the original condition of the location.

A running record of every person who enters or leaves the scene, with name, agency, time, and reason. It supports chain of custody and shows the scene was controlled.

The introduction of foreign material or DNA into a scene or sample, or the transfer of evidence between items. It can mislead analysis and is prevented by gloves, clean tools, and controlled access.

The location where the criminal act actually occurred, as opposed to a secondary scene where related activity happened later, such as a vehicle used for transport or a dump site.

Any location connected to the offense other than where the principal act took place, for example a body dump site, a getaway vehicle, or a suspect's residence. It may hold different evidence.

The initial walk-through in which the investigator observes the whole scene, notes conditions, identifies evidence and hazards, and plans a systematic search and documentation strategy.

A planned route for examining an area, such as line, grid, spiral, or zone search, chosen to suit the terrain and evidence type. It ensures the area is covered without gaps or duplication.

A search method in which the area is swept in parallel lines and then swept again in perpendicular lines. The double pass reduces the chance of missing small items.

A search method using a row of searchers who move forward together at a set spacing, used for large open areas such as fields or roadsides. Spacing depends on the item sought.

A search that moves either inward toward a center point or outward from it in widening circles. It suits contained areas and a single searcher working around a focal item.

A scale drawing of the scene showing the position of objects, evidence, and measurements relative to fixed reference points. It supplements photographs by recording spatial relationships.

A quick freehand drawing made at the scene that records measurements, item locations, and orientation. It is later used to produce a finished scale drawing for reports and court.

A method of locating evidence by measuring at right angles from a straight reference line between two fixed points. It allows each item's position to be plotted accurately on a sketch.

A record of each photograph taken at a scene, including frame number, subject, direction, distance, and photographer. It links images to their location and supports later testimony.

A wide view showing the scene and its surroundings as a whole, taken before closer images. It establishes context and the relationship of the scene to nearby buildings, roads, or landmarks.

A view showing an item of evidence together with its immediate surroundings, such as a weapon beside a chair. It bridges the overall and close-up views in a photo series.

A detailed image of an item or injury that fills the frame and usually includes a scale. It records identifying features, marks, and condition for later comparison and analysis.

A ruler or marker placed beside an item in a photograph to give size reference. It should sit in the same plane as the item so measurements taken from the image are accurate.

A lamp emitting specific wavelengths, such as ultraviolet or blue light, used with filters to reveal latent biological stains, fibers, or treated surfaces not visible under normal lighting.

Placing collected items in suitable containers, such as paper bags, envelopes, or rigid boxes, sealed and labeled with case details. Packaging choice prevents loss, degradation, and cross-transfer.

Material of human or animal origin such as blood, saliva, semen, hair, or tissue. It is prone to degradation and contamination, so it is air-dried, packaged in breathable containers, and stored cool.

A set of genetic markers from a biological sample that can be compared with reference samples or databases. It is powerful for identification but says nothing about when or how a sample was deposited.

A known sample taken from a person, object, or location for comparison with questioned evidence, such as a buccal swab, fingerprints, or known paint from a vehicle panel.

A fingerprint or palm print left by sweat and oils that is invisible to the naked eye. It is developed with powders, chemicals, or light techniques and then photographed or lifted.

A fingerprint visible without development because it was made in a substance such as blood, ink, grease, or dust. It is documented by photography before any treatment is attempted.

A method of developing latent prints on non-porous surfaces by brushing on fine powder that adheres to residue, then lifting the print with tape onto a labeled card.

Fingerprints collected from people known to have handled objects at the scene, such as residents or responders, so their prints can be excluded from the questioned latent prints.

Marks left by contact between objects, including footwear, tire, tool, and bite marks. Examiners compare class and individual characteristics to link a mark to a specific source.

Filling a three-dimensional impression, such as a shoe print in soil, with plaster or dental stone to preserve its shape and detail. The cast is then labeled and compared with known items.

The study of the size, shape, and distribution of bloodstains to infer events such as impact, dripping, transfer, or cast-off. It can suggest the direction, force, and position of a source.

The stiffening of muscles after death that begins within hours and later resolves. Its stage can help estimate time since death, though temperature, activity, and body size affect it.

The settling of blood in dependent parts of the body after death, producing a purplish discoloration. Its pattern and whether it blanches under pressure can inform position and timing estimates.

The gradual cooling of a body after death toward ambient temperature. Measuring body and environmental temperature helps estimate the postmortem interval, especially in the early hours.

The estimated time elapsed since death, derived from body temperature, rigor, livor, decomposition, insect activity, and scene context. It is always a range rather than a precise moment.

The use of insects and their life stages on a body to estimate time since death and to infer whether a body was moved. It requires expert collection of specimens at the scene.

Forming a reasoned account of what happened by combining scene observations, evidence analysis, witness statements, and reconstructive testing. It is a hypothesis tested against all available data.