I assume Jim and Bill have common authority over the closet, so the search of the closet itself was OK. Did the police say that they could see the outline of the murder weapon before they went thru the pockets? Had anyone been arrested?
I don’t think an answer to these questions exist in the abstract. Certainly not based upon assumptions, though. It’s like RNATB says - the facts are either there or they aren’t, and based on those facts there’s either an argument for common authority or there isn’t. Some people have a reasonable expectation of privacy for some coats in some houses, and others don’t.
Well, the facts are what they are. There is no evidence to suggest common control over the jacket or no evidence against it either.
Coolidge v. New Hampshire is instructive. A man convicted of murder was moving to suppress clothing of his that his wife provided to police. The clothing was tested and confirmed the presence of gunpowder residue. The Court with little struggle upheld that part of the evidence against him.
There was no discussion of the wife’s authority over his clothes and it seemed a non-issue. Of course, husband and wife is a different relationship than letting your buddy stay at your house. One could argue that his wife had authority over his clothes because she regularly washed them, but a counter would be that he gave her only that limited authority over his clothes. Also she is not acting as an agent of the state when she does this.
So it would seem like if Jim had searched the jacket and handed the incriminating stuff to the police, it would be allowed without question.
I also read Georgia v. Randolph and that goes into further detail. The majority and the dissent take pains to say that when you share property with another then you risk exposing it. If you share documents or conversations or leave things in plain view in a common area, you risk having that exposed.
Roberts said that if you don’t want something revealed, then put it in a locked briefcase under the bed in a private room. That still wouldn’t stop the wife in Coolidge from turning it over, and I’m not sure why it would be significant if it was in a locked briefcase in a private bedroom. If it is in a private bedroom, customary standards say that it is still my private stuff. Likewise, if I leave my wallet or a woman leaves her purse in the common areas. There is no explicit or even implied authority that a roommate can look into those things.
Likewise, if I leave my jacket in a hall closet, that’s not an open invitation for my other roommates to pilfer through it. There is a risk that such a thing may happen, but it wouldn’t be something that a reasonable officer would think gives the other roommate the authority to allow a search.
Imagine a coatroom at a restaurant. It is a common area. I have my coat hanging there. Would it be reasonable for an officer to think I had the authority to consent to the search of any coat on the rack?