What should be tested to eliminate suspect candidates in a suicide investigation?

In the context of a suicide investigation, testing for gunshot residue is critical to determining whether a suspect was involved in the shooting incident. Gunshot residue (GSR) is a byproduct created when a firearm is discharged, containing microscopic particles that can be deposited on the hands, hair, or clothing of a shooter. Therefore, if a suspect is found to have gunshot residue on them, it could indicate their potential involvement in the shooting scenario.

Identifying relevant evidence to narrow down suspect candidates is vital in a suicide investigation. Testing for gunshot residue helps investigators assess whether a person could have physically fired the weapon used in the incident. If a suspect's hands or clothing reveal the presence of GSR shortly after the incident, this may eliminate them as a candidate for suicide. Conversely, the absence of GSR could support the assertion that the individual did not discharge a firearm and may not be involved in the investigation.

The other options, while important in various investigative contexts, do not serve the same purpose in specifically eliminating candidates in a suicide investigation as efficiently as gunshot residue analysis.