Summary

William J. Brennan, Jr. Ker v. California — Concurrence-dissent

The first is that any exception not requiring a showing of such awareness necessarily implies a rejection of the inviolable presumption of innocence. The excuse for failing to knock or announce the officer's mission where the occupants are oblivious to his presence can only be an almost automatic assumption that the suspect within will resist the officer's attempt to enter peacefully, or will frustrate the arrest by an attempt to escape, or will attempt to destroy whatever possibly incriminating evidence he may have. Such assumptions do obvious violence to the presumption of innocence.
Source: Wikisource

William J. Brennan, Jr. Ker v. California — Concurrence-dissent

If mere police experience that some offenders have attempted to destroy contraband justifies unannounced entry in any case, and cures the total absence of evidence not only of awareness of the officers' presence but even of such an attempt in the particular case, I perceive no logical basis for distinguishing unannounced police entries into homes to make arrests for any crime involving evidence of a kind which police experience indicates might be quickly destroyed or jettisoned.
Source: Wikisource

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