Based on United States v. Hensley, police can stop a suspect at gunpoint when there is a clear threat to the officer's personal safety. In the Alvarez case, the police were justified in responding to a tip from an informant used by one of the officers in the past. This is a stronger case than obtained in the case of an anonymous phone tip in Adams v. Williams. Although the search following the stop in Alvarez revealed evidence of other crimes with which the defendant was charged, there was no reason, independent of the informer's statement, to believe Alvarez went to the bank parking lot for the purpose of robbing the bank, or that he was carrying explosives. Police have the authority to investigate and enter premises without a warrant in emergency situations that involve threats to life or property. For related chapters, see NCJ 115711-13.