Final answer:
Ammunition residue must be collected and turned in for both safety, handling regulations and to maintain the integrity of a forensic investigation, providing evidence that can link a suspect to a firearm or crime scene.
Step-by-step explanation:
Ammunition residue must be collected and turned in because it may contain commercial chemical products that are unused and could pose a health or environmental hazard if not properly disposed of. In a forensic context, especially during the investigation of a crime involving firearms, the collection of ammunition residue can provide crucial evidence. This residue can indicate whether a firearm has been recently discharged and by comparison of residue samples, it might link a suspect to the weapon or the scene.
Furthermore, there are strict regulations and protocols regarding the handling of such residues since they can contaminate crime scenes or inadvertently be transferred to other objects or people. In addition to safety and legal reasons, the appropriate handling of ammunition residue aids in maintaining the integrity of an investigation, ensuring that all physical evidence is meticulously analyzed to deliver the justice that is due.