This article examines the role of expert testimony in police misconduct litigation. Police practices experts have become particularly conspicuous in cases alleging use of excessive force, and their participation in cases may fundamentally change the nature of the litigation. By virtue of their bearing the label of expert, their testimony and opinions tend to be particularly influential on juries. Expert testimony can alter the fact-finding process and be both “powerful and quite misleading.” Experts are afforded “extraordinary credence,” and so it is essential for law enforcement managers and their attorneys to be cognizant of the legal and strategic issues that relate to relying on or defending against police practices experts.

In police use-of-force litigation, there can be a proper role for a police practices expert, provided that expert and his or her methodology and opinions satisfy the applicable legal standards. An expert witness may be used either to offer an opinion based on his expertise or to present testimony that is factual in nature but relies on some specialized knowledge. Expert testimony and opinion evidence are admissible if that evidence is helpful to the jury. Generally, appropriate expert testimony relates to (1) the merits of a case, (2) causation issues, or (3) the amount of damages.