term:

Useless Gesture Exception

useless gesture exception n

: an exception to the knock and announce rule that excuses police from having to announce their purpose before entering a premises in execution of a warrant if facts known to the officers justify them in being virtually certain that the occupant already knows their purpose

Source: Merriam-Webster's Dictionary of Law ©1996. Merriam-Webster, Incorporated. Published under license with Merriam-Webster, Incorporated.