So I'm reading this book about criminal law and ran across this little gem I'm sure we'll all be glad to know...
This is Bob. Bob has an ex-wife and a cocaine stash. Bob may not be terribly bright either, but that's beside the point.
(The book is providing a case example to illuminate some of the finer details involved in a search and seizure:)
Bob's ex-wife Jan knows where Bob hides his cocaine. She calls the police and tells them about the cocaine. She directs them to Bob's house. When they get there, she opens the door with a key (she never gave it back to him). She puts her purse on the entry hall table, opens the hall closet and puts on a sweater that appears to be hers. She then leads them to the place where Bob keeps his cocaine. As far as the police know, Jan lives in the apartment and has full authority to consent to the search.
So basically, even though the police totally did not have this dude's permission, this search did not violate Bob's Fourth Amendment right because the police were right to believe Jan had the authority to consent to the search.
Ain't that a bitch.
But really, if you're that stupid not to move your stash one you've established an enemy who knows where you keep it, then you deserve to be busted, I suppose.