Deadly Force

Deadly force is a force that a person uses causing or that a person knows or should know would create a substantial risk of causing death or serious bodily harm or injury. In most jurisdictions, the use of deadly force is justified only under conditions of extreme necessity as a last resort, when all leaser means have failed or cannot reasonably be employed.

Firearms, bladed weapons, explosives and vehicles are among those weapons the use of which is considered deadly force. The use of non-traditional weapons in an offensive manner such as a baseball bat, sharp pencil or tire iron may also be considered deadly force.

United States Law
In the United States, the use of deadly force by sworn law enforcement officers is lawful when the officer reasonably believes the subject poses a significant threat of serious bodily injury or death to themselves or others. The use of deadly force by law enforcement is also lawful when used to prevent the escape of a fleeing felon when the officer believes escape would pose a significant threat of serious bodily injury or death to members of the public. Common law allowed officers to use any force necessary to effect a felony arrest but this narrowed in the Tennesse v. Garner ruling in 1985 when the U.S. Supreme Court said that "deadly force...may not be used unless necessary to prevent the escape and the officer has probable cause to believe that the suspect poses a significant threat of death or serious bodily harm to the officer or others".