Police and correctional officers may use various levels of force to gain compliance, make arrests, and protect themselves and others. The Supreme Court ruled in Tennessee v. Garner that deadly force is only justified to protect against death or serious harm, rather than to stop all fleeing felons. An officer's perception can be distorted by stress, leading them to "see" things that aren't there, especially for black suspects due to racial stereotypes. Training aims to reduce these effects of stress.