Deadly force, as defined by the United States Armed Forces, is the force which a person uses, causing—or that a person knows, or should know, would create a substantial risk of causing—death, 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 lesser 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 nontraditional-weapons in an offensive manner, such as a baseball bat, sharp pencil, tire iron or other, may also be considered deadly force.
"Use of deadly force" is often granted to police officers when the person or persons in question are believed to be an immediate danger to people around them. For example, an armed man flaunting a firearm in a shopping mall without regard to the safety of those around him, and refusing or being unwilling to negotiate, would warrant usage of deadly force, as a means to protect others. The use of deadly force is also authorized when a person poses a significant threat to a law enforcement officer, usually when the officer is at risk of serious bodily injury or death. In the United States, this is governed by Tennessee v. Garner, (U.S. Supreme Court 1985) which 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." This case abolished the Fleeing felon rule where a fleeing felon who posed no immediate threat to society (e.g., a burglar) could be shot if they refused to halt.
In Graham v. Connor, (U.S. Supreme Court 1989) the court expanded its definition to include "objective reasonableness" standard—not subjective as to what the officer's intent might have been—and it must be judged from the perspective of a reasonable officer at the scene—and its calculus must embody the fact that police officers are often forced to make split-second decisions about the amount of force necessary in a particular situation.
Most police agencies establish a use of force continuum and list deadly force as a force of last resort. With this model, agencies try to control excessive use of force. Nonetheless in the United States there are a high number of killings by law enforcement officers.
In the United States, a civilian may legally use deadly force when it is considered justifiable homicide, that is to say when the civilian feels that their own life, the lives of their family, or those around them are in legitimate and imminent danger.
In all advanced countries the law requires an investigation whenever a civilian or law enforcement officer uses deadly physical force that causes someone's death. This may include determining whether the officer's use of deadly physical force was appropriate under the relevant standards established. For example, in the United States an investigation is usually performed by a larger police agency and/or a civilian agency, such as a county prosecutor or State Attorney General. A report of the findings of such an investigation may be submitted for prosecution and made public.
Use of deadly force in relation to motor vehicles: In Scott v. Harris, No. 05-1631 (April 30, 2007). , the (U.S. Supreme Court 2007) held that a police officer’s attempt to terminate a dangerous high-speed car chase that threatened the lives of innocent bystanders did not violate the Fourth Amendment, even when it places the fleeing motorist at risk of serious bodily injury or death. In the Harris case, Officer Scott applied his police car's push bumper (PIT maneuver—Pursuit Immobilization Technique) to the rear of the suspect's vehicle, causing the suspect vehicle to lose control and crash, resulting in the fleeing suspect being paralyzed from the waist down.
Traditionally, intentional contact between vehicles has been characterized as unlawful deadly force, though some U.S. federal appellate cases have mitigated this precedent. In Adams v. St. Lucie County Sheriff’s Department, 998 F.2d 923 (11th Cir. 1993). , the Seventh Circuit Court of Appeals ruled that although fatalities may result from intentional collisions between automobiles such fatalities are infrequent, and therefore unlawful deadly force should not be presumed to be the level of force applied in such incidents; the Adams case was subsequently called into question by Harris v Coweta County, 406 F.3d 1307 (11th Cir. 2005). , which in turn was reversed by the U.S. Supreme Court in the Scott v. Harris case discussed above; the extent to which Adams can continue to be relied on is uncertain. In the Adams case, the officer rammed the suspect's vehicle.
In Donovan v. City of Milwaukee, 17 F.3d 944 (7th Cir. 1994). , the Seventh Circuit Court of Appeals recognized this principle but added that collisions between automobiles and motorcycles frequently lead to the death of the motorcyclist, and therefore a presumption that unlawful deadly force was used in such intentional collisions is more appropriate. In the Donovan case, the suspect lost control of his motorcycle and became airborne, crashing into the officer's vehicle, which was parked as part of an intercepting roadblock.
- AFI 31-207 Arming and Use of Force by Air Force Personnel
- Robert C. Ankony, "Sociological and Criminological Theory: Brief of Theorists, Theories, and Terms," CFM Research, Jul. 2012, p.37.
- "Use of Deadly Force by Law Enforcement Officers". Chief Attorney. February 1, 2008. Retrieved 28 December 2013.