No Knock Search Law and Legal Definition

No knock search refers to the search of a property by the police without knocking and announcing their presence and purpose before entering into the property. In other words, it is a a search warrant that allows law enforcement officers to enter premises without prior announcement in order to prevent destruction of evidence or harm to the officers.

In United States v. Mattison, 153 F.3d 406 (7th Cir. Ill. 1998), it was observed that a no-knock search is justified when there is a reasonable suspicion that knocking and announcing the police officers' presence would be dangerous or futile, or that it would inhibit the effective investigation of the crime.