The police officer's legal authority to use deadly force is set forth and defined by common law, statute, and case law. Traditional common law allows use of deadly force when apprehending someone reasonably believed to have committed a felony. Since there has been an expansion of crimes considered felonies, and the use of death penalty has decreased, many States have enacted statutes stricter than common law. The courts have challenged the use of deadly force when lives are not threatened, and civil suits filed against police departments and individual officers have risen. Despite concerns about establishing an increased basis for civil liability, the clear trend across the country seems to be toward the adoption of department firearms use policies. These policies vary widely in scope. Many simply repeat State laws governing use of deadly force while others are narrower. Many allow police use of deadly force only when there is reasonable certainty that a felony has been committed and when there is reasonable assumption of a threat to life. Departmental policies govern such areas as self-defense and defense of others, shooting at fleeing felons, shooting at juveniles, the threat to innocent bystanders, shooting from or at a moving vehicle, firing of warning shots, the drawing and display of firearms, and the use of shotguns and second guns. A clearly stated policy removes much of the uncertainty surrounding many situations and can help to resolve subsequent legal issues. One table, 23 footnotes, and a list of 8 references are included.