The 4th: Third party consent
In many situations, two or more people reside at a residence and thus have concurrent expectations of privacy. In this situation, the courts have held that a third party can give consent to search even if the defendant has refused the search, as long as the third party had an expectation of privacy in that area.[1]
Case Law
“Third party consent may be given by one who has common authority over or some other sufficient relationship to the premises or effects being searched. Common authority does not require common ownership, but merely ‘mutual use of the property by persons generally having joint access or control for most purposes, so that it is reasonable for the searching officers to believe that the person granting consent had the authority to do so.’ However, a homeowner may grant consent to search the premises on which a criminal defendant resides if the homeowner possesses common authority over or sufficient relationship to the premises or effects to be inspected.” State v. Flowers, 360 S.C. 1, 5–6 (Ct. App. 2004)

[1] State v. Flowers, 360 S.C. 1, 5–6 (Ct. App. 2004)