Very interesting, thanks. Follow up question: if the girlfriend had said something like "There's a camera in the closet that recorded all this, and he'll probably erase it when you leave" - do you think that would have been sufficient to make it not a fourth amendment violation? The idea being that they were told about it by the victim, rather than searching for it.
My read of the precedent is that when it comes to the invoking the destruction of evidence exception, the exigency must be imminent. If the girlfriend had said there was video tape of the beating, it would take very little time to get a warrant signed. This happened in San Francisco, and a big city like that will have magistrate judges on call 24/7. Meanwhile, if the police were lawfully on the premises to ensure her safety, they not only could lawfully detain him while waiting to get a warrant, but had probable cause to arrest him for domestic violence. My read is that courts favor a short detention like this over a warrantless search.
I suppose that if she had called and just said: "he's going to delete tapes showing him beating me" they would have exigent circumstances to enter to prevent destruction of evidence, even if the circumstances were such that they didn't otherwise have exigent circumstances to enter to prevent bodily injury. But that's somewhat contrived.
