At 7:30 p.m. Seattle narcotics officer Belland received information from a confidential informer, a narcotics user, that certain persons were smoking opium in a hotel. The informer, after returning to the hotel, said that he could smell burning opium in the hallway. Belland and four narcotics agents, all of whom were experienced in narcotics work, went to the hotel between 8:30 and 9 p.m. All agents recognized the unmistakably strong odor of opium, which led them to Room 1, whose occupant(s) was then unknown to the officers. The officers knocked on the door, and, when asked who was there, responded “Lieutenant Belland.” After a short delay, Johnson (defendant) opened the door. When told that the officer wanted to talk to her, Johnson “stepped back acquiescently and admitted us.” Asked about the opium smell, Johnson denied that there was such a smell. She was then told, “I want you to consider yourself under arrest because we are going to search the room.” She did not consent to the search. In the subsequent search, opium and a still-warm smoking apparatus were found, indicating recent use. The district court refused to suppress this information, and Johnson was convicted of having violated federal narcotics laws. The court of appeals affirmed.