One primary legislative cause of the difficulties in prosecuting police is the 1986 the United States supreme courts case, Tennessee v. Garner, which did not allows usages of deadly force by an officer unless "the officer has a good-faith belief that the suspect poses a significant threat of death or serious physical injury to the officer or others" but the rhetorically vague term "good-faith belief" allowed an objective reason to kill and created a barrier in proving an officer is guilty in court system. While this old legislative piece accounts the difficulties in prosecuting police, the traditional unspoken rule of police officers not to report against colleagues cause corruption in the process of prosecution which is another source of