The U.S. Constitution prohibits police officers from using unreasonable force in performing their duties. The determination of what constitutes "reasonable" force is based on the unique, practical considerations facing the officer. Force can be lawfully used by law enforcement officers either in response to a threat or to effect the seizure of a nonthreatening subject. Officer response to these two justifications can be different; training and policies should emphasize this distinction. Policymakers and trainers must focus on core use-of-force principles. First, policies and training must focus on overcoming instinctive hesitation in using force, not encouraging it. Second, there never can be "bright-line" rules for the use of force; every use-of-force situation is unique. Third, the cornerstone of use-of-force training must be threat assessment. Fourth, officers must be trained to respond to the threat of violence and not to the actual violence itself. Finally, use-of-force responses to the two force justifications are very different. When there is a threat, officers must be trained to not hesitate and to be able to deploy reasonable force quickly. 41 notes