In law enforcement, a knock and talk is an investigative technique where one or more police officers approaches a private residence, knocks on the door, and requests consent from the owner to search the residence. The knock and talk is often performed when criminal activity is suspected, but there is not sufficient evidence to obtain a search warrant.
In the United States
The legality of the knock and talk procedure has been carefully scrutinized and reviewed by American courts at the state and federal level. Rulings in both the Ninth Circuit case United States v. Cormier and Seventh Circuit case United States v. Jerez have held that evidence obtained from a consensual search following a knock and talk is admissible, but only if the knock and talk is not conducted in a coercive or aggressive manner.