Crime Scene Reconstruction and Trace Evidence

The scientific evaluation of physical evidence and other reliable information to develop and test explanations of events surrounding a crime.

Determining the possible order of actions or events from their physical relationships and other evidence.

A testable explanation of how an event may have occurred based on available evidence.

Reconstruction evaluates evidence to infer events; reenactment demonstrates a proposed sequence using people, objects, or models.

A proposed reconstruction should be compatible with reliable physical findings and account for significant contradictory evidence.

A competing explanation that investigators evaluate to determine which account best fits the evidence.

An association established when separated fragments fit together through corresponding broken edges or other distinctive physical features.

Corresponding irregular fracture features may support the conclusion that fragments were once part of the same object.

Small quantities of material transferred or deposited during an event, such as fibers, glass, paint, soil, or particles.

It may establish or support associations among people, objects, and locations.

Direct movement of material from its source to another person, object, or surface.

Indirect movement of material through an intermediate person, object, or surface.

Transferred material may be lost or redistributed over time, affecting whether it remains available for examination.

A comparison sample collected from an appropriate source or unaffected area to help evaluate questioned material.

Class characteristics associate evidence with a group; sufficiently distinctive features may support a more specific association.

A glass particle whose source or relationship to a relevant object is under investigation.

A measure of how light changes direction when passing through glass, useful in comparing certain glass samples.

Differences in density may help distinguish glass samples, although matching density alone does not establish a common source.

To compare chemical composition and assess whether questioned and known glass samples are distinguishable.

A crack extending outward from an impact region.

A crack extending around an impact region, often forming roughly circular or curved paths.

The rule that radial fractures form right angles on the reverse side of the force, subject to fracture conditions and limitations.

Glass type, support, impact conditions, and fracture complexity may prevent reliable application.

A later fracture may terminate at a preexisting fracture, providing information about their relative order.

No. Complex cracking, secondary breakage, and incomplete recovery can limit interpretation.

It may support an association with a glass-breaking event, subject to transfer, persistence, and alternative-source considerations.

The comparison and characterization of paint materials to assess possible associations with objects or locations.

Layer sequences, colors, thicknesses, and chemical compositions may provide more discriminating information than surface color alone.

The order of coating layers present in a paint sample, which can be compared with a suspected source.

A complete sample permits comparison of the coating structure rather than only its outermost layer.

To examine infrared absorption patterns that help characterize or compare certain chemical materials.

A technique used to measure optical absorption or transmission characteristics of very small samples, including colored fibers.

The examination of fiber characteristics to assess whether questioned and known fibers are distinguishable or consistent.

Fibers originating from biological sources, such as cotton, wool, and silk.

Fibers produced through industrial processes, such as polyester, nylon, and acrylic.

The observable physical structure of a fiber, including diameter, cross-sectional shape, and surface characteristics.

Many textiles contain fibers of similar colors, so additional physical and chemical characteristics must be considered.

A mark produced when a tool contacts a surface and leaves an impression of its features.

A mark containing linear features produced when a tool moves across a surface under contact.

A mark formed when a tool presses against a surface with little or no sliding movement.

Features shared by a subset of tools because of manufacturing processes, which may be mistaken for more distinctive features.

They can create similarities between different tools and must be distinguished from features supporting a specific-source conclusion.

A mark produced under controlled conditions with a known tool for comparison with questioned marks.

To examine corresponding surface features of questioned and known marks under comparable magnification and lighting.

Directly documented physical findings and proposed explanations have different levels of evidentiary certainty.

The absence of an expected finding may challenge a hypothesis when the evidence should reasonably have been present and detectable.

The fragments likely originated from the same object, while the circumstances of separation require additional evidence.

No. The association must be assessed alongside possible transfer routes, timing, and independent evidence.

The crack that terminates may have formed after the crack it meets, provided the fracture pattern is suitable for sequencing.

Reevaluate the account and reconstruction, investigate the contradiction, and avoid forcing the evidence to fit a preferred explanation.