what is trace evidence
Tiny fragments of physical evidence left at or exchanged from a crime scene including from a victim or suspect.
examples: hair, fibers, paint and glass
How is trace evidence analyzed?
Trace evidence is typically analyzed based on its physical and chemical properties.
Value of Trace Evidence
most trace evidence is unable to directly link or identify an individual or specific object.
Value of fiber evidence
The rarity or commonness of the fiber determines its usefulness in an investigation.
Class characteristics
- Class Characteristics are properties of physical evidence that can be associated only with a group and never with a single source. …
Examples of class evidence includeblood type, fibers, and paint to name a few.
Individual Characteristics
Properties of physical evidencethat can be attributed to a common source with a high degree of certainty.
example dna toolmarks and fingerprint
Direct Transfer
From victim to suspect or from suspect to victim – Ex. from suspect’s sweater to victim
Secondary Transfer
- When fibers are transferred from an original source to one person and then to a second person.
Fiber classification
Natural fibers are derived entirely from animal or plant sources whereas
manufactured fibers are derived from natural or synthetic polymers and number in the hundreds.
Synthetic fibers are/can:
Stronger than natural fibers.
Not damaged by microorganisms.
Often cheaper than natural fibers.
destroy in bright sunlight & melt at lower temperatures.
Have very regular diameters under magnification.
several methods used in the laboratory to identify natural and manufactured fibers
- Microscopic examination
- Dye composition analysis
- Chemical composition
