James Mandarino, Suburban Chicago Police Officer, Stands Trial For Beating Motorist (VIDEO)

01/24/2011 11:10 am ET | Updated May 25, 2011

A police officer from the Chicago suburbs stands trial Monday for a ruthless beating captured on his own squad car's dashboard video camera.

James Mandarino, a Streamwood police officer, is charged with aggravated battery and official misconduct for the beating of 28-year-old Ronald Bell.

Bell and a friend, Nolan Stalbaum, were driving home from an Ultimate Fighting Championship match last April, according to the Chicago Tribune. They were stopped by Mandarino, who followed them a few blocks to Bell's driveway.

Bell pulled up to his house, and Stalbaum got out of the car. But Mandarino emerged from his patrol car, firearm drawn, and Bell got back into the driver's seat. The officer then used his stun-gun on Stalbaum, who was already out of the car, making him collapse in a heap on the stairs.

For a few minutes, Mandarino speaks to Bell -- the video has no sound, but Bell appears docile and compliant. Then, with Bell on his knees, hands behind his head, Mandarino starts relentless beating Bell with his metal baton, hitting him 15 times before he collapses to the pavement.

All this is captured on the video camera in Mandarino's squad car. Still, according to NBC Chicago, the officer's union lawyer claims he is denying any wrongdoing.

Bell and Stalbaum have also filed a federal lawsuit against Mandarino.

Watch the video of the beating: