Many of the lawyers on the show break multiple laws, Matlock included. They investigate people without a warrant and sometimes without probable cause, and break into places. There are several instances of violence either caused by them or because of them. Matlock even breaks attorney-client privilege multiple times. Though legal themes are sound, any of them could have lost their license, and it's just glossed over and ignored. This happens throughout the show.
Multiple cases of reused footage from in front of the Atlanta Police Department.
Prison and jail cells are frequently shown without toilets in them. In the United States of America, the vast majority of jail cells and all prison cells have toilets in them.
Exterior shots frequently show mountains and palm trees, none of which can be found in Atlanta.
Not counting two-part episodes and stories without court appearances, there are approximately 165 cases over eight years in which Matlock has his client found not guilty and also exposes that the District Attorney's office had arrested the wrong person. In any actual DA's office, these statistics would be devastating to a prosecutor, would show extreme incompetence on the part of the courts and the police, and probably lead to federal intervention due to the astronomical number of false and improper arrests.