Where an officer faxed a probable cause statement to a magistrate over the weekend and received a faxed finding of probable cause in return, the defendant’s Fourth Amendment rights were not violated because the procedure satisfied that amendment’s requirement that “no Warrants shall issue, but upon probable cause, support by Oath or affirmation.” After first determining that the fax procedure satisfied federal law, the court turned to the constitutional issue and found no violation. The probable cause statement was signed under penalty of perjury, which the Ninth Circuit held qualified as an “affirmation” even if it could not qualify as an oath under the terms of the amendment. The court rejected the defendant’s argument that an affirmation could only be made in person, holding that by giving his written statement under penalty of perjury, the declarant knew that he was making a solemn promise to the magistrate that all the information he was providing was true and correct, and that is all that the Fourth Amendment’s “Oath or affirmation” clause requires.