<P> A civilian's use of deadly force is generally justified if he or she reasonably believe that he or she is or other innocent lives are in imminent danger of death or serious injury . Justification and affirmative defenses vary by state and may include certain property crimes, specific crimes against children or prevention of sexual assaults . </P> <P> U.S. law requires an investigation whenever a person causes another person's death, but the mechanism for such investigations can vary by state . The investigation develops evidence regarding the use of deadly physical force for the particular state or jurisdiction . An investigation may performed by a local or state police agency and also 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 . </P> <P> 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 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 . </P> <P> 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 . </P>

When are you allowed to use deadly force