An exigent circumstance allows law enforcement to enter a structure without a warrant, or if they have a "knock and announce" warrant, without knocking and waiting for refusal, under certain circumstances. It must be a situation where people are in imminent danger, evidence faces imminent destruction, or a suspect will escape. Exigent circumstances are: Even in exigent circumstances, while a warrantless seizure may be permitted, a subsequent warrant to search may still be necessary.