Is a police officer required to stop at the door of a house to knock and announce their purpose?

Furthermore, stopping to knock and announce their purpose would not have furthered the purpose behind section 1531. As explained in People v. Peterson (1973) 9 Cal.3d 717, 108 Cal.Rptr. 835, 511 P.2d 1187, "[S]tatutes requiring announcement serve the following purposes and policies: '(1) the protection of the privacy of the individual in his home [citations]; (2) the protection of innocent persons who may also be present on the premises where an arrest is made [citation]; (3) the prevention of situations which are conducive to violent confrontations between the occupant and individuals who enter his home without proper notice [citations]; and (4) the protection of police who might be injured by a startled and fearful householder.' " ( Id. at p. 723, 108 Cal.Rptr. 835, 511 P.2d 1187.) None of these purposes would have been served by requiring the officers to stop at the front door, knock, and again announce their purpose.