People v. Thompson
In People v. Thompson, 770 P.2d 1282 (Colo. 1989), the Supreme Court of Colorado determined that exigent circumstances were present where police responded to an anonymous call of on-going domestic violence. When police arrived on the scene, they observed several spent .38 caliber casings on the driveway and blood on the front porch, on the front door, and on the side of the house next to the front door.
The front door was ajar several inches, and glass in the front door was shattered and completely broken around the doorknob. A woman came to the door with obvious injuries and announced, "He's gone, everything's o.k." and then shut the front door and locked it.
The officers however entered the residence by reaching through the hole in the door's glass and unlocking the door.