A police officer for the Maryland Transit Administration pleaded guilty in federal court on Wednesday to mail fraud in a scheme to burn three vehicles owned by transit employees for the insurance money. According to his plea agreement, James Walthall, 41 years old, of Randallstown falsely reported in February of year 2003 that his 1997 Ford Expedition had been stolen and filed a fraudulent insurance claim. In April 2003, Walthall burned or had someone else burn the vehicle in an attempt to conceal his insurance fraud, according to court documents. Walthall now faces a maximum of 20 years in prison.