Part one demonstrates that, in response to increasing criminal violence in the 1960's and 1970's, police began to employ more sophisticated defensive tactics in search and seizure situations. Police officers learned that quickly asserting control over potentially violent confrontations is crucial to safe and successful police operations. Part two examines how the spread of drug trafficking and violent street gangs has redefined the threat of criminal violence to police. Part three argues that the threat to police in high-risk narcotics search warrant service and the tactical imperatives of speed and control balanced against privacy interests call for re-evaluating knock and announce law. Part four concludes that the no-knock warrant is a legal tool whose time has come. Allowing the use of a justified defensive measure such as the no-knock entry to address the hazards of high-risk warrant service, but subjecting such entry to screening magistrate review, will serve both competing law enforcement and privacy interests more effectively. 92 references.