What is the first action to take when a detective relieves an officer during a preliminary investigation?

The correct action in this situation is to brief the detective. This step is crucial because the detective needs to be informed about the current status of the investigation, including any details regarding evidence collected, witness statements, and the overall scene assessment. A thorough briefing allows the detective to quickly understand the context, make informed decisions on how to proceed, and ensures continuity in the investigation process.

In a preliminary investigation, it is vital that information flows accurately between officers and detectives to maintain the integrity of the case. This briefing not only helps in maintaining operational efficiency but also enhances communication within the law enforcement team, ensuring that all pertinent information is conveyed effectively to support the ongoing investigation.