IAI SP4 key terms

A chronological written record of every person who has handled, transferred, or stored an item of evidence, showing dates, times, purposes, and signatures so its integrity can be demonstrated in court.

A closure or tape applied to a package so that any opening or interference leaves visible damage, with the sealer's initials, date, and seal number recorded on the packaging and in the chain-of-custody log.

Selecting a container and method that protect an item from loss, contamination, and degradation while allowing safe transport and storage, such as paper bags for damp biological items and rigid containers for sharps.

The condition in which an item's identity, quantity, and condition are unchanged from collection to presentation, demonstrated through complete documentation, secure storage, and an unbroken custody record.

The proposition that contact between two objects usually results in transfer of material from one to the other, which underpins the search for trace evidence at scenes and on persons.

Small or microscopic materials such as hairs, fibers, glass fragments, paint chips, soil, or gunshot residue whose presence may link people, objects, and locations, requiring careful collection to avoid loss.

Material moving directly from its source to a receiving surface through a single contact, as when fibers from a sweater adhere to a victim's clothing during a struggle.

Material that moves from its original source to an intermediate object and then to a third surface, which can complicate interpretation of how evidence came to be where it was found.

A sample of the unstained or unaffected material adjacent to a questioned deposit, collected so analysts can distinguish the stain's profile from background substances present in the item itself.

Material of unknown origin collected for comparison, such as a stain, hair, or fragment, which is tested against known reference samples to determine whether a common source is supported.

Material of established origin taken from a person, object, or location for comparison with questioned evidence, collected with documented consent or legal authority and handled to prevent contamination.

Introduction of exogenous genetic material into a sample through handling, speaking, coughing, or dirty tools, which can create misleading profiles and is prevented by gloves, masks, and single-use instruments.

Practices for safely managing potentially infectious biological evidence, including gloves, eye protection, designated packaging, labeling, and decontamination of tools and work surfaces.

Air-drying damp items such as bloodstained clothing at room temperature before packaging in paper, because sealing moisture promotes bacterial growth and mold that degrade DNA and other markers.

The outer boundary established around a scene to control access, keep unauthorized persons out, and preserve evidence, typically set wider than the apparent area of interest and adjusted as the scene is assessed.

A running record of every person entering or leaving a controlled scene, with name, agency, purpose, and times, used to identify potential contamination sources and support testimony about scene control.

The initial systematic walk-through in which investigators observe the overall scene, identify hazards, note conditions, and plan a search strategy before detailed documentation and collection begin.

A planned route for examining an area, such as line, grid, spiral, or zone methods, chosen to suit the terrain, number of searchers, and type of evidence sought so that no area is overlooked.

A hand-drawn, not-to-scale diagram made at the scene showing the layout, fixed reference points, and measured positions of evidence, later used to prepare a final scaled drawing.

A measurement method that locates an item by recording distances from two fixed reference points, allowing its position to be reconstructed accurately on a scaled diagram.

A documentation technique in which a straight reference line is established between two fixed points and each item's position is recorded by right-angle distance along and away from that line.

Records written at or near the time of an observation, capturing dates, times, conditions, and actions in enough detail that the investigator can testify accurately months or years later.

The use of cameras and controlled lighting to create accurate, undistorted images of scenes, evidence, and injuries that document conditions and support analysis and courtroom presentation.

A wide view showing the scene or item in context, including surrounding features and landmarks, taken before closer views so the relationship of evidence to the environment is preserved.

An intermediate view that shows an item of evidence together with its immediate surroundings, bridging the context of overall images and the detail of close-up images.

A detailed image of a specific item or injury, usually with a scale and label in frame, taken to show size, pattern, and identifying characteristics for analysis and comparison.

A ruler or labeled marker placed beside evidence in a photograph so that size and position can be verified, positioned in the same plane as the subject to avoid perspective error.

Change in apparent shape or size caused by lens choice, camera angle, or subject placement, minimized by keeping the film or sensor plane parallel to the subject and avoiding wide-angle lenses for evidence.

An invisible or barely visible fingerprint deposited by sweat and oils from friction ridge skin, made visible through powders, chemical reagents, or alternate light sources.

A fingerprint or footwear impression visible to the naked eye because it was made in a medium such as blood, ink, dust, or grease, documented photographically before any enhancement attempt.

Marks left when one object presses into or onto another, including footwear, tire, tool, and bite marks, preserved by photography, casting, or lifting depending on the surface and material.

Pouring a setting material such as dental stone into a three-dimensional impression to produce a positive replica that preserves detail for examination and comparison.

Applying a flexible gelatin or similar sheet to a surface to lift a dry or powdered impression or latent print, then transferring it to a contrasting backing for preservation and examination.

The characteristics of friction ridge skin used in comparison, including ridge flow, ridge endings, bifurcations, dots, and pores, assessed in combination rather than by simple counting.

Specific ridge features such as endings, bifurcations, islands, and enclosures whose locations and relationships are compared between a latent print and a known print.

A comparison methodology with four stages: analysis of each print's quality and features, comparison of their features, evaluation of whether differences are explainable, and verification by an independent examiner.

Independent re-examination of a comparison by another qualified examiner who reaches a conclusion without knowledge of the first examiner's result, used to test and strengthen the finding.

Technical review of casework, reports, or conclusions by a qualified colleague outside the original examination, intended to detect error and confirm that methods and documentation meet laboratory standards.

Periodic testing of examiners with known or blind samples to demonstrate competence in specific techniques, required by accreditation programs and used to identify training needs.

Formal recognition that a laboratory meets published quality standards through external assessment of its management system, personnel, methods, equipment, and records.

Opinion evidence given by a witness qualified by training and experience to assist the court in understanding specialized matters, subject to challenges about qualifications, methods, and reliability.