A violation of the knock-notice rule does not require suppression of evidence found during the search. Where police entered a home with a warrant but without complying with the rule that they first knock and announce their presence, the Fourth Amendment does not require suppression of the evidence. The illegal entry did not cause the discovery of evidence, and even if it had caused that discovery, the causal connection would be too remote to justify suppression of the evidence. The interests protected by the knock-notice rule – protection of life and limb, protection against property destruction – have nothing to do with the seizure of evidence, and thus the social costs of excluding evidence outweigh the value of possibly deterring illegal police conduct.