In what circumstances will the court allow evidence to be used in a search?

In Frazier v. Cupp (1969) 394 U.S. 731, 740, 89 S.Ct. 1420, 1425, 22 L.Ed.2d 684, the defendant challenged the admissibility of evidence found during a search of a duffel bag left at his cousin's house which he and his cousin used and which his cousin consented to be searched. In holding the joint use of the duffel bag gave his cousin the authority to consent to the search, the court was unwilling to engage in the "metaphysical subtleties" raised by the defendant's claim that his cousin only had permission to use one compartment within the bag. Because the defendant had allowed his cousin to use the bag, and had left it in his house, the defendant assumed the risk his cousin would let someone else examine it.