Federal and State jurisdictions permit the use of deadly force when "immediate" threats to life exist, but universal recognition of this legal principle has not led to universal attention to the practical realities that are essential to realistic and uniform application. The resulting inconsistencies and confusion only increase the dangers that already attend law enforcement. The U.S. Supreme Court recognized in Graham v. Connor that officers often must make "split-second judgments" concerning the use of force under "circumstances that are tense, uncertain and rapidly evolving ..." In assessing the constitutionality of an officer's use of deadly force, the Supreme Court in the same case set the standard of "objective reasonableness." This means that the reasonableness of a particular use of force must be judged from the perspective of a "reasonable officer on the scene, rather than with the 20/20 vision of hindsight." In assessing the reasonableness of an officer's use of deadly force, only the perceptions of the officer are relevant to the standard of reasonableness. Facts unknown to the officer, such as whether or not the suspect actually had a weapon, cannot be used to determine the reasonableness of the officer's action. The concern that officers be discouraged from using excessive force is legitimate, but this concern must be balanced against the equally legitimate interest in permitting law enforcement officers to protect themselves and others during the performance of hazardous duties. The "objective reasonableness" standard permits officers to protect themselves based on their assessment of the threat in the immediacy of the circumstances. 20 footnotes