Potter Stewart

“ When the constitutional validity of an arrest is challenged, it is the function of a court to determine whether the facts available to the officers at the moment of the arrest would 'warrant a man of reasonable caution in the belief' that an offense has been committed. ”

“ In complete contrast, the record in this case does not contain a single objective fact to support a belief by the officers that the petitioner was engaged in criminal activity at the time they arrested him.
An arrest without a warrant bypasses the safeguards provided by an objective predetermination of probable cause, and substitutes instead the far less reliable procedure on an after-the-event justification for the arrest or search, too likely to be subtly influenced by the familiar shortcomings of hindsight judgment. ”

“ Ohio, 367 U.S. 643, 81 S.Ct. 1684, 6 L.Ed.2d 1081, the clearing house slips were wrongly admitted in evidence against him because they had been seized by the Cleveland police in violation of the Fourth and Fourteenth Amendments. 376 U.S. 905, 84 S.Ct. 664, 11 L.Ed.2d 604.
Although the police officers did not obtain a warrant before arresting the petitioner and searching his automobile and his person, the Supreme Court of Ohio found the search nonetheless constitutionally valid as a search incident to a lawful arrest. ”