What must be done to a firearm's cylinder before it is collected as evidence?

When collecting a firearm's cylinder as evidence, it is essential to indicate its position because this detail can provide valuable information related to the incident. The position of the cylinder can affect how the firearm operated during the event, such as whether it was loaded or unloaded at the time, and which round was in line to be fired. This information is critical for forensic analysis and can influence the investigation.

Documenting the cylinder's position ensures that no evidence is altered or lost in the process of collection. It also establishes a clear context for the evidence, which can be vital during legal proceedings. Photographs or notes should be made to accurately reflect the position before any further handling or changes occur.