In general, the primary resident of a home can give valid consent to a search even if it might implicate a guest who is temporarily staying there. But if the resident doesn’t have access to or use of the place or item to be searched, the consent is probably invalid.
Example: Badger asks Jesse for permission to stay in the latter’s home. Jesse agrees and Badger moves some belongings in temporarily. When Drug Enforcement Administration agents come knocking, Jesse consents to their searching the house. During the search, they find an open bag in the living room with “Badger” stitched into it and baggies of methamphetamine exposed. The drugs are likely admissible in court against Badger since, as a mere guest, he didn’t have a legitimate expectation of privacy in the living room. (Turner v. State, 573 So. 2d 657 (Miss. 1990).)
On the other hand, if the officers had found the bag in a room that Jesse had set aside specifically for Badger, and only Badger had used and had access to that room during the visit, then the evidence might be inadmissible. (State v. Cover, 450 So. 2d 741 (La. Ct. App. 1984).)
Furthermore, regardless of its location, if the bag had been zipped shut and the officers had discovered the meth only after opening it, a court would probably suppress the evidence. That’s because hosts generally don’t have the authority to consent to a search of their guests’ “personal effects” when there’s no reason to believe they have access to or control over them. (State v. Edwards, 214 Conn. 57 (1990), People v. Gonzalez, 88 N.Y.2d 289 (1996), People v. Loomis, 794 N.Y.S.2d 220 (2005).)
For information about a guest's authority to agree to a search of a home, see Can a houseguest give consent for a search of my home?