another police procedure question

A judge authorizes a search warrant. No one else has any say.

Searching the dorm room would provide vital clues as to possible suspects and motives for the murder. It's probably one of the first places the police would search if they know the identity of the victim. Although a search warrant would be needed to keep the chain of evidence intact.

If a victim is killed away from his residence, a search warrant would be needed to search that residence, but the probable cause exists with the crime, and is a no-brainier for the judge. However, there must be suspicious circumstances to the death. If the person stepped off the curb and was hit by a bus, the investigation might begin and end at the scene of the accident.

I have known people in a shared living situation - specifically, young adults in group home living, which is similar to a dorm, because unrelated young people are sharing a living space. The police were allowed to search the shared room for evidence, but a staff security officer and the girl's roommate were present for the search, and the police were not allowed to touch anything the roommate identified as belonging to her, unless they came back with another search warrant.