Which of the following indicates that a person's body could be found in a scene of investigation?

A dead body is a definitive indication that a person's body is present at a scene of investigation. When law enforcement or investigators encounter a deceased individual, it establishes a clear focus for the investigation, including determining the cause of death, the circumstances surrounding the death, and any potential criminal activity involved.

The other options suggest various circumstances but do not confirm the presence of a remaining body at a scene. A coroner's case refers to the legal process following a death that may not yet be investigated in person, a missing person indicates that an individual is unaccounted for, and "man down" generally signifies a person who may require assistance but does not necessarily confirm that the individual is deceased. Therefore, encountering a dead body provides a straightforward and concrete point of investigation.