by John Marshall Harlan

“ Clearly, it is said, they had probable cause for believing that the passengers in the car were the men described in the bulletin, and, in acting on the bulletin, they reasonably assumed that whoever authorized the bulletin had probable cause to direct Whiteley's and Daley's arrest. To prevent arresting officers from acting on the assumption that fellow officers who call upon them to make an arrest have probable cause for believing the arrestees are prepetrators of a crime would, it is argued, unduly hamper law enforcement. ”

“ We do not, of course, question that the Laramie police were entitled to act on the strength of the radio bulletin. Certainly police officers called upon to aid other officers in executing arrest warrants are entitled to assume that the officers requesting aid offered the magistrate the information requisite to support an independent judicial assessment of probable cause. Where, however, the contrary turns out to be true, an otherwise illegal arrest cannot be insulated from challenge by the decision of the instigating officer to rely on fellow officers to make the arrest. ”

“ The State urges us to remand so that it will have an opportunity to develop a record which might show that the issuing magistrate had factual information additional to that presented in Sheriff Ogburn's complaint. Brief for Respondent 8-9. Yet the State concedes, as on the record it must, that at every stage in the proceedings below petitioner argued the insufficiency of the warrant as well as the lack of probable cause at the time of the arrest. ”