When Ben is shown driving just before being run off of the road, he is not wearing his seat belt in any of the shots. During an exterior shot of the car going off of the road, you can see the driver is now wearing his seat belt. After Ben has crashed and the car is lying on its right side, Ben is laying the up against the right-hand door (his position is incorrect and covered elsewhere in Goofs) and is again without his seat belt.
When Matlock comes upon the disabled truck, it is pulled over on the opposite side of the road. The driver, Ramon, says he is headed to his new job, just up the road. Matlock offers to give him a ride the rest of the way, but continues with Ramon in his car without turning around. He would have been taking Ramon further from his job by doing so.
When Matlock was supposed to be in his car just before he was chased down by the pickup, the driver obviously wasn't Ben Matlock.
When Matlock was talking on the policeman's radio, he failed to use the button on the microphone.
When the camera shows Matlock lying in his car after being forced off the road, the position of the car is incorrect. Matlock is lying on his side, with his head against the armrest in the door, but the car itself is lying on its side. If Ben was actually in this position, he would not be lying on the seat.
When Ben is driving on his way to go fishing, there are several shots that show snow-capped mountains rising some 12,000' above the valley floor. What you see behind Ben is the Sierra Nevada Range, a 400-mile long group of mountains that sit West of the Owens Valley in California. One of the mountains that you see is Mt. Whitney, the highest mountain in the Continental United States at 14,505'. The highest elevation in Georgia is at Brasstown Bald, at an elevation of 4,784'. It is given that Ben is not supposed to be in California as the signage in the small town he gets stranded in shows Georgia on numerous buildings and signs.
Ben acts like he had never heard of the famous U.S. v. Leon case before. It was one of the Supreme Court's landmark cases and every lawyer would have been very familiar with it. What's more, Julie tells Ben that U.S. v. Leon was decided "late last year" when in fact it had been decided about eight years before in 1984.