Lawyers for former Detroit Mayor Kwame Kilpatrick say dozens of interviews have failed to turn up any evidence he obstructed the investigation into the slaying of a stripper who was sprayed with bullets in a drive-by shooting in 2003.

After dozens of depositions over several months, no witness has “confirmed any relevant and admissible material fact that Kwame Kilpatrick either personally, or by agreement, obstructed, impeded and interfered or directed others to obstruct … the investigation,” attorneys James Thomas and Michael Naughton wrote.

The court filing describes how the case moved from the police department’s homicide division to a cold case squad to the desk of the Wayne County prosecutor, then back to cold case and, finally, a multi-agency task force. Authorities believe they know who killed Greene, but they don’t have enough evidence to charge him. He’s in prison for another crime.