How is gunshot residue typically collected from a suspect?

Gunshot residue (GSR) is typically collected from a suspect by using tape lifts or swabs to capture any residue from the hands. This method is effective because GSR particles are often very small and can easily be transferred to a suspect's skin or clothing after discharging a firearm.

Using tape lifts enables for the collection of residue from uneven surfaces and can capture particulates without losing them, while swabs can be used in a more controlled manner, allowing for a precise collection from specific areas, such as the palms or fingers. This method preserves the integrity of the evidence and minimizes contamination, which is crucial for forensic analysis.

The other methods mentioned are not considered standard practice for collecting gunshot residue. For instance, using cotton balls and water might introduce moisture that could alter or destroy the residue. Similarly, using a vacuum cleaner lacks the specificity needed for GSR collection and may inadvertently remove vital evidence. Scraping off residues, although it may seem like a direct approach, carries the risk of losing important fine particles or damaging the evidence. Hence, tape lifts and swabs are the preferred methods for efficiently and safely collecting gunshot residues.