The Supreme Court has held that a grand jury witness offered immunity is not entitled to a suppression hearing and may not refuse to answer questions based on evidence obtained in an illegal search.
United States v. Calandra, 414 U.S. 338 (1974).
Robert S. Adams,
Constitutional Law - Fourth Amendment - Search and Seizure - Exclusionary Rule - Grand Jury,
Duq. L. Rev.
Available at: https://dsc.duq.edu/dlr/vol13/iss1/14