"M.O." is an abbreviation of the Latin phrase modus operandi, which roughly translated means "method of operation". In Criminology, this means the way by which someone has perpetrated/committed a crime.
case
The witnesses and the victims.
The forensic team were at the scene of the crime investigating.
DEBORAH JERMYN has written: 'CRIME WATCHING: INVESTIGATING REAL CRIME TV'
. . . The Forensic Crime Scene Technician or the Investigating Detective.
Until the investigating agency has released it and no longer needs it to gather or recover evidence.
A moulage can be used to make of mold of shoe or tire impressions and then be used for comparison of suspect's shoes or vehicle when investigating a crime.
When you investigate crime, it is always possible that the criminal whom you are investigating may violently object.
"all the people on the train kill him but the ones investigating the crime"
When the investigating officials have deemed the scene no longer necessary for the collection/preservation of evidence
what route you took to the scene
Act fairly and follow established rules.