Federal constitutional standards permit police officers to use deadly force to apprehend criminal suspects when there is "probable cause to believe that the suspect poses a threat of serious physical harm to the officer or to others" and if deadly force "is necessary" to effect the apprehension. Legal challenges on this issue have argued that deadly force was not necessary because less intrusive alternatives were available; or if deadly force was necessary, the officer's prior actions created the necessity. The U.S. Supreme Court has held that reasonableness under the fourth amendment does not require police officers to choose the least intrusive alternative, only a reasonable one. Following this principle, most courts have rejected arguments that the use of deadly force was not necessary because officers had less intrusive options available or it was made necessary by the actions of the officers themselves. These decisions that limit potential liability claims should encourage police policymakers to continue to develop appropriate policies and procedures to guide officers in the use of deadly force without undue concern that those initiatives will become weapons in the hands of litigants. 24 notes