PHILADELPHIA—A suspended Philadelphia Traffic Court judge has pleaded guilty in federal court to mail fraud and income tax evasion charges just as his trial was getting underway.

Fifty-six-year-old Robert Mulgrew agreed Thursday in U.S. District Court to plead guilty in exchange for all related charges being dropped against his wife.

Prosecutor Paul Gray said Mulgrew stole tens of thousands of dollars in state grant money that was earmarked to clean up a park and vacant lots in his South Philadelphia neighborhood.

He will be sentenced later.

Mulgrew is also charged in a separate case with ticket fixing. About a dozen people are charged in that case and Mulgrew, who has pleaded not guilty, is still awaiting trial there.