“ Such a theory is of course absurd, but this absurdity does not mean that Bryant was threatening to harm the President. A vast gap separates the conclusion that a letter warning of an assassination threat is preposterous or delusional and the conclusion that the letter, itself, constitutes a threat by the author. Even if a delusional warning may serve to identify the author as mentally unstable and justify appropriate surveillance of his activities, such legitimate concern does not transform a delusional warning into a threat. ”

“ As I suggested at the outset, the confusing set of facts may well have justified a trained officer in coming to the conclusion that a mentally unstable person might pose a threat to the President's well-being. No matter how reasonable such an officer's belief may have been, that kind of suspicion is not a substitute for a reasonable determination that the evidence established probable cause to arrest.
The District Court denied the petitioners' motion for summary judgment seeking dismissal on the ground of qualified immunity because it decided that further fact-finding was necessary. ”

“ Whether a reasonable officer could have believed he had probable cause is a question for the trier of fact, and summary judgment or a directed verdict in a § 1983 action based on lack of probable cause is proper only if there is only one reasonable conclusion a jury could reach. ”