Can a witness refuse to answer questions at a grand jury?

In United States v. Calandra, 414 U.S. 338, 94 S.Ct. 613, 38 L.Ed.2d 561 (1974), it held that a grand jury witness could not refuse to answer questions because they were based on information obtained in violation of his Fourth Amendment rights. Because the evidence would be suppressed in a subsequent criminal proceeding, application of the rule "would deter only police investigation consciously directed toward the discovery of evidence solely for use in a grand jury investigation." Id. at 351, 94 S.Ct. at 621.