A while back I was asked if I could analyze Georgia v. Randolph on CrimLaw. I couldn't at the time because I was judging a moot court argument with this as one of its questions. The question? When there is a common shared area (but exclusive to others) and one of the persons sharing the area refuses to consent to a police search can the other person give consent while the first person is present? In other words, can permission from one resident overcome prior denial by the other resident when both are present?
The poor kids doing the first session I judged got me, Tom (Seeking Justice), and the head prosecutor from Richmond's south side (Manchester). While every other contestant was getting questioned by civil lawyers (posing as judges) these kids had a little bit of a hot bench. The second session was just me and Tom and those kids might have actually had it a little rougher. They all did fine; I just felt sorry for them pulling the only criminal lawyers that were judging.
Anyway, Orin has addressed theory with far more depth than I have time to cover here. However, here are the rules of thumb which I think most courts have found:
1) If there are multiple residents of a house each resident can give permission to search if the other resident is not present.
2) The person giving permission cannot give absolute permission. If there is some thing or place which is restricted from the person giving permission (i.e. a forbidden room, an unshared safe, a computer with files that the permittor cannot access) then permission does not extend to a search of it.
3) The standard applied is not solely whether the permittor has actual authority; the standard is whether the permittor had actual or apparent authority. Hence, police can rely on Mom's permission to search her adult child's room, even if she has not gone in the room for two years. A search reliant on the claims of a woman that she is a daughter of the accused (and who opens the door with a key) would be valid even if she were only the nosy neighbor who had found the emergency spare (unbeknownst to the police). However, when a male gives permission to search that will not extend to the female resident's purse. Likewise, the search of the room above should not be valid if the door were locked and mom told the police she didn't have a key.
All that said, I think the standard which has been assumed for a long time is that if a person with authority gives permission it is valid against all comers. When we were discussing the moot court arguments with the law students in the after argument critique everybody was commenting on how the pro-Randolph argument was the "loser" argument.
Personally, I think the equities are in favor of the Randolph decision. Allowing the police to do what they did in this case is to allow them to game the system. Of course, they could have gamed the system anyway by asking to search when he wasn't present. And police gaming the system hasn't exactly been a powerful argument in recent years (see any of my various rants about Whren sanctioned clearly pretextual stops). It'd be nice if the Court stepped up and said, "The Constitution does not directly address this question and when there is an ambiguous area that relates to personal rights guaranteed under this document we must always err in favor of protecting the citizen against the overwhelming power of the State. Therefore, we find the search unconstitutional." It'd be nice, but I'm not holding my breath.