r. Its compulsory processes stand available to require the presentation of evidence hucourt or before a grand jwy. United States R. Nixon, supra; Kastigar R. United States, 406 U.S 441, 443444. S.Ct. 1653, 1f5-1616, 32 L.Ed.2d (1972); Murphy . Waterfront Comm'n, 8 U.S. 52, 93- 4, 84 S.Ct. 1594, 1610-1611, 12 L.Ed