Authorities say he drove for five miles on Evansville's west side with a dog tied to the back of a truck.
Cox says he didn't know the dog, a Great Dane named Hank, was attached to the bumper.
This just happened in May, and his trial started Wednesday.
Jamie McFarland, is accused of tying Hank to the bumper.
He's also facing charges.
The trial is expected to wrap up on Thursday.