Final answer:
A separate PD 81 form is required when firearms are involved, as they are highly regulated items in criminal investigations and require meticulous documentation to preserve the integrity of evidence and follow the due process of law.
Step-by-step explanation:
The question pertains to the PD 81 form and the specific circumstances under which a separate one is needed. The PD in this context likely refers to Police Department protocols for documentation and procedures regarding the handling of incidents. Given the options presented, the correct situation that would require a separate PD 81 form and can is C) Firearms are involved. This is supported by the scenario provided and also aligns with the requirements for maintaining chain of custody and documentation for evidence, especially when it comes to firearms, which are highly regulated items in criminal investigations.
As seen in the scenario where suspects are involved in armed robbery and unlawful weapon possession, the separation of cases and the meticulous documentation is necessary to ensure that the due process of law, as stated in the Fifth Amendment, is followed. Furthermore, handling firearms requires specific procedures to ensure safety and preserve the integrity of evidence, which may necessitate additional forms and separation from other criminal matters being investigated or documented simultaneously.