The corruption trial of Kilpatrick, his father Bernard and Bobby Ferguson, a longtime friend of the former mayor, resumed Thursday after a 12-day Christmas break, The Detroit News reported.
Much of the testimony Thursday centered on how Bernard Kilpatrick allegedly underpaid his taxes, as well as his gambling habits.
The Kilpatricks and Ferguson are facing a number of charges, including alleged bid-rigging and kickbacks.
IRS agent Rowena Schuch testified she believed the older Kilpatrick underpaid his taxes by a total of $184,000 in 2004, 2005 and 2007 by hiding income from the government.
Schuch also said Bernard Kilpatrick lost about $218,000 while gambling at casinos in Detroit and Las Vegas.
The elder Kilpatrick was former Wayne County Executive Edward McNamara's chief of staff before he left to start consulting firm Maestro Associates in 2002, when Kwame Kilpatrick took office.