Trace Evidence contends that every contact, no matter how slight, will leave a trace. The trace is normally caused by objects or substances contacting one another, and leaving a minute sample on the contact surfaces. Material is often transferred by heat induced by contact friction.
Collection of trace evidence may be achieved by using tweezers, swabs, electro-static lifters or by casting impressions, among other things. Invisible evidence, such as bodily fluids, can be detected using an ultraviolet lamp and then collected by swabbing. Luminol is often used to discover the presence of blood, as blood will start to glow when sprayed with this chemical.
Once collected, trace evidence is analyzed in the lab, and the results are entered into a database.
Types of Trace
- Blood droplets or residue
- Bodily fluids (i.e. saliva, semen, etc.)
- Skin particles
- Car scraps
- Bomb parts