Which of the following is considered trace evidence?

Trace evidence refers to small pieces of material that can be transferred from one location or object to another, and typically includes items that are not easily visible or that may be present in tiny quantities. This type of evidence is critical in linking a suspect to a victim or crime scene.

Samples of insulation are regarded as trace evidence because they can originate from specific locations and can be transferred during a crime, offering significant insights into the circumstances surrounding that event. Insulation can be examined for various characteristics, aiding in determining whether a suspect was at a particular site.

In contrast, expended shell casings generally represent more substantial physical evidence rather than trace evidence. Gunpowder residue can also be significant but is typically analyzed as a type of chemical residue rather than trace evidence in the traditional sense. Dried saliva swabs tend to be considered biological evidence, as they consist of bodily fluids collected for DNA analysis rather than trace materials transferred indirectly.