The Detroit Police Department spent 13 years under federal oversight after a U.S. Department of Justice investigation in 2000 alleged police for decades had practiced unconstitutional policing. Federal authorities say Detroit cops had a pattern of using excessive force, sometimes resulting in deaths, and routinely arrested witnesses who had committed no crime. Innocence advocates say this practice of rounding up witnesses and leaning on them until they told detectives what they wanted to hear resulted in numerous wrongful convictions.