Here's an interesting 4th Amendment case for you. The facts: Cops suspect a guy of child porn. They drive to his house, where he lives with his dad. Dad, home alone, answers the door. The cops ask if they can search the home and any computers there, the dad consents. Warrantless searches with consent are valid to the extent of consent. The cops find a computer, take it to the station, and search the hard drive using forensic software. That search turns up child porn.
But there's a catch - the computer had different user accounts, and one account couldn't access the other account's files. So the dad would log in under dad's account, and couldn't see the son's child porn.
So, is the search valid?
It's a 10th Circuit case, US v Andrus, which upheld the search on the dad's apparent authority. That means that the cops could rely on the authority of the dad as it appeared to them - they thought he could authorize it, so the search is valid. The dissent views the porn files as inside a locked container. That is, they are deserving of greater privacy protection and the cops couldn't pick the locks.