SPOKANE, Wash. -

A retired federal judge has been hired by the City of Spokane to investigate the circumstances leading up to Scott Stephens being placed on administrative leave from the Spokane Police Department.

Mayor David Condon announced Monday Judge Michael Hogan has been retained to investigate why Stephens, who served as interim police chief and assistant chief, was placed on administrative leave by Chief Frank Straub on Dec. 20.

As of Monday Stephens remains on administrative leave.

Stephens was placed on leave the day before Straub announced sweeping change to his department's command staff, re-assigning Stephens to the lower rank of lieutenant from his position as assistant chief, while promoting Major Craig Meidl to assistant chief.

At the time of the announcement on Dec. 21, Stephens, who had served as acting chief following Anne Kirkpatrick's resignation and Frank Straub's hiring, was being reassigned to take charge of improving training techniques within the department.

The City of Spokane worked with Judge Hogan last spring, when he served as the mediator between the city and the Estate of Otto Zehm. That mediation resulted in a settlement between both parties.

"This is a sensitive personnel matter during a time of transition that required some diligence to explore a mutually acceptable resolution," Mayor Condon said in a written statement about the Stephens case.

Hogan will begin his investigation into Stephens being placed on administrative leave on Wednesday and is expected to be completed by the end of March.