"As a general rule, police officers enjoy immunity from civil liability for conduct committed in the course of the performance of their duties. Unless the facts suggest an exception, officers are entitled to pre-trial dismissal of civil suits rising out the official conduct. The immunity extends even to instances where the officer's conduct is unconstitutional or otherwise unlawful as long as the conduct does not 'violate clearly established statutory or constitutional rights of which a reasonable person would have been aware.' The 'clearly established' law need not be directly on point but must place the question beyond debate so that the immunity 'protects all but the plainly incompetent or those who knowingly violate the law.'"
CRS Legal Sidebar, February 9, 2017
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html