“ Under settled law, Secret Service agents Hunter and Jordan are entitled to immunity if a reasonable officer could have believed that probable cause existed to arrest Bryant. Probable cause existed if "at the moment the arrest was made . . . the facts and circumstances within their knowledge and of which they had reasonably trustworthy information were sufficient to warrant a prudent man in believing" that Bryant had violated 18 U.S.C. § 871. ”

“ This accommodation for reasonable error exists because "officials should not err always on the side of caution" because they fear being sued. Davis, supra, 468 U.S., at 196, 104 S.Ct., at 3020. Our national experience has taught that this principle is nowhere more important than when the specter of Presidential assassination is raised. ”

“ Another employee said that the man who delivered the letter made statements about " 'bloody coups' " and " 'assassination,' " and said something about " 'across the throat' " while moving his hand horizontally across his throat to simulate a cutting action. Id., at 718-719.
Hunter and another Secret Service agent, Jeffrey Jordan, then visited a local address that appeared on the letter. Bryant came to the door and gave the agents permission to enter. He admitted writing and delivering the letter, but refused to identify " 'Mr. Image' " and answered questions about " 'Mr. ”