As mentioned before, suspects dictate the level of force which is used to effect their arrest and the outcome of the incident. There are times when suspects do the opposite of what you tell them to do. The suspect might make a quick or furtive movement, forcing you to make one of those split-second decisions.
The question then becomes whether the plaintiff's quick or furtive movement, combined with the totality of the information known to the officers, was sufficient to lead the officers to reasonably believe the plaintiff posed an imminent threat of death or serious injury. In some cases the answer will be yes. If the answer is yes, then the use of deadly force by the officers is justified.
This is supported by Sherrod vs. Berry, 856 F.2d 802, 807 (7th Cir. 1988) where the court said deadly force was justified despite a weapon not being seen and where the suspect made a "quick movement with his hands into a coat."
The Fourth Circuit also upheld an officer involved shooting where the officer mistakenly believed the suspects were reaching for a weapon. (Elliot vs. Leavitt, 99 F. 3d 640, 642-43 (4th Cir. 1996).
In police shooting cases, the Ninth Circuit has consistently interpreted Tennessee vs. Garner, 471 U.S. 1 (1985) as authorizing deadly force where a suspect poses reasonable threat of death or serious injury to the officer or others. In citing Garner, the Ninth Circuit has concluded, "an officer's use of deadly force is reasonable if the officer ahs probable cause to believe that the suspect poses a significant threat of death or serious physical injury to the officers or others."