In the U.S. Supreme Court ruling of District of Columbia v. Heller, the majority held that the Constitution protected the right to the possession of firearms for the purpose of self-defense "and to use that arm for traditionally lawful purposes, such as self-defense within the home".Two other forms of justifiable homicide are unique to the prison system: the death penalty and preventing prisoners from escaping. To quote the California State Penal Code (state law) that covers justifiable homicide:

196. Homicide is justifiable when committed by public officers and those acting by their command in their aid and assistance, either--1. In obedience to any judgment of a competent Court; or,2. When necessarily committed in overcoming actual resistance to the execution of some legal process, or in the discharge of any other legal duty; or3. When necessarily committed in retaking felons who have been rescued or have escaped, or when necessarily committed in arresting persons charged with felony, and who are fleeing from justice or resisting such arrest.Although the above text is from California law, many other jurisdictions, like Florida, have similar laws to prevent escapes from custody. Examples include self defense, prevention of criminal act, trespassers, and defense of another person. Notable cases involving justifiable homicide
Killing of MaKhia Bryant.
In 1874, Muybridge shot and killed Major Harry Larkyns, his wifes lover, but was acquitted in a controversial jury trial, on the grounds of justifiable homicide. Johnny Stompanato homicide. After four hours of testimony and approximately 25 minutes of deliberation, the jury deemed Stompanatos killing a justifiable homicide. Further reading
Omphemetse S. "Use of Deadly Force by the South African Police Services Re-visited". == References ==