In the past year, 15 states have enacted laws that expand the right of self-defense, allowing crime victims to use deadly force in situations that might formerly have subjected them to prosecution for murder. Supporters call them "stand your ground" laws. Opponents call them "shoot first" laws. As a result of this sort of law, a prostitute in Port Richey, Fla., who killed her 72-year-old client with his own gun rather than flee was not charged last month. Similarly, the police in Clearwater, Fla., did not arrest a man who shot a neighbor in early June after a shouting match over putting out garbage, though the authorities say they are reviewing the evidence. The first of the laws took effect in Florida in October, and cases under it are reaching prosecutors and juries there.