IAI Footwear key terms

The arrangement of grooves, blocks, and ribs molded into the bottom of a shoe sole. Its design, dimensions, and wear create the impression examiners compare between a crime scene and a known shoe.

The bottom-most layer of a shoe that contacts the ground. It carries the tread design and is the surface that usually produces the impression recovered at a scene.

The layer between the outsole and the upper, usually made of foam or rubber, that provides cushioning. Its shape and any exposed sidewall markings can appear in three-dimensional impressions.

Random, acquired features such as cuts, tears, nicks, and embedded stones that develop on a shoe during wear. They can support an identification beyond what the manufactured tread pattern alone allows.

The areas of a sole that are worn thin or smoothed by the owner's gait and use. It is useful for narrowing a possible source and for comparing a questioned impression with a specific shoe.

Features shared by a whole group of manufactured items, such as a tread design, size, or brand. They can include or exclude a shoe but cannot by themselves identify one specific shoe.

Features unique to one specific shoe, such as particular cuts, wear, or embedded debris. When reproduced in an impression, they support an opinion that a particular shoe made that impression.

An impression made under controlled conditions from a specific shoe or tire, used as the comparison standard. It may be collected as a test print, a gel lift, or a scan of the item itself.

An impression of unknown source recovered from a scene or item and submitted for examination. The examiner evaluates it for quality, then compares it with known impressions or reference databases.

A print made deliberately from a known shoe or tire, often with ink or powder, to capture the full tread and any individual features for side-by-side comparison.

A print left when a shoe or tire transfers a contaminant such as blood, mud, or dust onto a surface. It records the outline and pattern but generally little depth information.

An impression pressed into a deformable material such as soil, snow, or wet cement. It records depth, tread edges, and sometimes sidewall detail, allowing casting or photogrammetry.

An impression that is not visible to the unaided eye, often left by clean soles on a hard surface through residue or slight surface change. It requires enhancement techniques to visualize.

A device that applies a static charge to a lifting film so dust and residue impressions transfer from a surface onto the film. It is widely used for dry, dusty footwear impressions on floors.

A sheet of gelatin-based material pressed onto an impression to transfer dust, residue, or a test print onto a stable backing. It preserves pattern detail for photography and comparison.

The process of pouring a material such as dental stone into a three-dimensional impression to produce a positive replica. The cast preserves depth and fine detail for later comparison.

A gypsum-based material favored for casting impressions because it sets hard, expands only slightly, and captures fine detail. It is mixed and poured according to controlled procedures.

Light directed at a low angle across a surface to reveal faint impressions, texture, and edge detail. It is a standard photographic technique for documenting footwear and tire evidence.

Systematic photographing of an impression before lifting or casting, including scale, orientation, and overall context. Proper photographs preserve the scene record and support later analysis.

The controlled collection of impression evidence, whether by photography, lifting, casting, or collecting the whole substrate. Correct recovery preserves detail and chain of custody.

The documented record of who handled evidence, when, and how it was transferred or stored. Gaps or errors can undermine the admissibility and weight of impression evidence.

The grooved rubber surface of a tire that contacts the road and provides traction. Its pattern, dimensions, and wear are the basis for comparing tire impressions.

A mark left by a tire, in dust, mud, blood, or a deformable surface. Examiners assess tread design, track width, wheelbase, and individual damage features.

The distance between the centerlines of the left and right tires on the same axle. It helps link a set of tire impressions to a vehicle class or a specific vehicle.

The distance between the front and rear axles of a vehicle. Measured from a series of tire impressions, it can narrow the possible make or model of the vehicle.

Raised bars molded into tire grooves that show when tread depth has worn to a minimum. Their presence and position can appear in impressions and aid identification.

A code molded into a tire's sidewall or tread that identifies the manufacturing mold. Tires from the same mold share class features useful in comparison.

The production tooling that forms a tread pattern. Shoes or tires made from the same mold share a pattern, so mold identity is a class characteristic rather than a unique one.

Numbers or letters molded or printed on a sole or insole indicating size and sometimes width. Size is a class characteristic that can include or exclude a candidate shoe.

Treatment of an impression with reagents or powders to increase contrast or reveal latent residue, such as blood or dust. The method chosen depends on the surface and suspected contaminant.

A collection of known tread patterns, such as manufacturer catalogs or an agency's shoe and tire files, used to identify a pattern of unknown source.

An instrument that presents two specimens side by side in one field of view. It allows an examiner to align tread features and assess similarities and differences.

Overlaying a questioned impression image on a known image, often digitally, to test whether pattern features align. It is one aid to comparison, not a substitute for examiner judgment.

Whether an impression contains enough pattern and detail to support a meaningful comparison. Poor sufficiency may limit an examiner to class-level conclusions or no conclusion.

Procedures such as peer review, verification, and documented protocols that check the reliability of an examination before a report or testimony is issued.

A defined set of opinion levels, such as identification, exclusion, or inconclusive, used to express comparison results consistently. It communicates the strength and limits of an examiner's finding.

A mark left by a shoe on a surface, whether visible or latent, two- or three-dimensional. It is examined for pattern, size, wear, and individual features.