to execute a search warrant, if, after notice of his authority and purpose, he is refused admittance or when necessary to liberate himself or a person aiding him in the execution of the warrant. (Emphasis added.) In the ordinary case an officer is required to state both his authority and his purpose. Miller v. United States, 357 U.S. 301, 308-09, 78 S.Ct. 1190, 1195, 2 L.Ed.2d 1332 (1958). In this case, however, the police, after knocking and announcing their authority repeatedly, but without eliciting a response, heard someone running down the back stairs. A reasonable interpretation of such sounds is that the inhabitants are well aware of the purpose of the police visit and are moving to destroy evidence. This is especially true where, as 1623, 1632-1634, 10 L.Ed.2d 726 (1963) (<HOLDING>). III. Thomas James argues that the evidence
recognizing the rule and the exception but holding facts did not support claim to exception recognizing exception recognizing difference in elements between offense of actual entry and attempted entry recognizing an exception to a california announcement and entry statute recognizing such an exception