What is the test for "exigent circumstances" in the context of search and seizure cases?

Exigent circumstances are "those circumstances that would cause a reasonable person to believe that entry (or other relevant prompt action) was necessary to prevent physical harm to the officers or other persons, the destruction of relevant evidence, the escape of the suspect, or some other consequence improperly frustrating legitimate law enforcement efforts. United States v. McConney, 728 F.2d 1195, 1199 (9th Cir.) (en banc), cert. denied, 469 U.S. 824 (1984). We review de novo the issue of the exigency. Id. at 1205.