Can a police officer enter a person's home without a warrant?

"One exigency obviating the requirement of a warrant is the need to assist persons who are seriously injured or threatened with such injury. ' "The need to protect or preserve life or avoid serious injury is justification for what would be otherwise illegal about an exigency or emergency." ' [Citations.] Accordingly, law enforcement officers may enter a home without a warrant to render emergency assistance to an injured occupant or to protect an occupant from imminent injury. [Citations.]" (Brigham City v. Stuart (2006) 547 U.S. 398, 403 [164 L.Ed.2d 650, 657-658].)