A Food Market was robbed by two men, one of whom was described by eyewitnesses as carrying a gun and wearing horn-rimmed glasses and a grey jacket. Soon after the robbery a checkbook belonging to D was found in an adjacent parking lot and turned over to the police. Two of the stubs in the checkbook indicated that checks had been drawn to the order of the Mayfair Hotel. The officers learned that D had a previous criminal record. They obtained from the Pomona police a photograph of D. They showed the photograph to the two eyewitnesses to the robbery, who both stated that the picture looked like the man who had carried the gun. The officers went to the Mayfair Hotel without any kind of warrants and asked the night clerk if there was a party by the name of D living at the hotel. He stated: 'Yes, there is.' They were told he was in Room 404 but D was out at this time. The officers asked the clerk for permission to enter the room. They explained that D had possibly committed a robbery and the officers were concerned about the fact that he had a weapon. The clerk gave permission and placed a key in the lock, unlocked the door, and said: 'Be my guest.' The officers searched the room and its contents. They found a pair of horn-rimmed glasses and a grey jacket in the room, and a .45-caliber automatic pistol with a clip and several cartridges in the bottom of a bureau drawer. D was arrested two days later in Las Vegas, Nevada. D tried to get the evidence excluded but the gun, the cartridges and clip, the horn-rimmed glasses, and the grey jacket were all used as evidence against him at his trial. D was convicted and appealed. The District Court of Appeal thought the search was justified as an incident to a lawful arrest. D appealed again.