An underworld informer advised a police investigator that his neighbor was running an illegal bookmaking operation in his apartment, and that the informer had placed bets with the neighbor at this location. The officer obtained a search warrant, based on his affidavit reciting the foregoing facts, and further stating that the underworld informer was a person who had given him accurate information in previous cases, but whose identity could not be revealed because it might jeopardize other criminal investigations being carried on by the police. Armed with the search warrant, police officers went to the neighbor’s apartment. They entered when the neighbor opened the door and searched the apartment. They seized various wagering slips and bookmaking apparatus (described in the search warrant) and placed the neighbor under arrest for illegal gambling. Prior to trial, the neighbor challenges the validity of the search warrant. Was the search warrant valid?