how is the firearm examined during a criminal investigation?
It is examined for serial numbers and potentially fingerprints.
Forensic firearm examination
For forensic firearm examination specific evidence that can be recovered include weapon serial numbers and potentially fingerprints left on the weapon's surface.
who published a study of tool marks on bullets UNANSWERABLE
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Forensic firearm examination [SEP] Examination of the firearm
Any firearm collected during the course of an investigation could yield viable evidence if examined. For forensic firearm examination specific evidence that can be recovered include weapon serial numbers and potentially fingerprints left on the weapon's surface.