(9th Cir.1986) (“The ultimate issue of whether exigent circumstances justify a warrantless entry and/or search is resolved under the de novo standard.”). “Where, as here, there are no explicit factual findings, the record below is assessed in the light most favorable to the trial court ruling.” Tibolt, 72 F.3d at 969. First, we reject Merced-Mor-ales’ argument that the search of his residence and automobile was unlawful in light of the agents’ failure to knock and announce. The Supreme Court has held: [F]or Fourth Amendment purposes, an arre is not without its exceptions. Specifically, entry without notice to execute an arrest warrant is permissible when notice would jeopardize the safety of the officers. See Ker v. California, 374 U.S. 23, 39-40, 83 S.Ct. 1623, 10 L.Ed.2d 726 (1963) (<HOLDING>); cf. Fletcher v. Town of Clinton, 196 F.3d 41,
holding that commonlaw knock and announce principle forms a part of the reasonableness inquiry under the fourth amendment holding that commonlaw knock and announce rule is part of the fourth amendment reasonableness inquiry holding fourth amendment not violated by failure to announce where compliance would have increased officers peril holding that noncompliance with nrs 179055 was justified where compliance with statute would have placed officers in great physical peril holding that arrest in backyard violated fourth amendment