When the man is murdered at the beginning, the body moves between shots.
At about the 30-minute mark when the cop wanted to arrest Ben, he makes the statement, "According to passport records yours are the only prints on the murder weapon." Passports do not require any fingerprints from US citizens, even today, unless you are going for TSA pre-check (or the like).
Mrs. Hawkins reads Ben his horoscope revealing him to be a Gemini (Andy Griffithwas in fact a Gemini) and gives him reasons as to Why he shouldn't go to defend this case. But if the characters (as Ben) shared the same signs as the actors playing them; the same would go for Michelle ( Nancy Stafford ) is also a Gemini) and as instructed later by Mrs. Hawkins's phone call telling Ben not to associate with Capricorns; He shouldn't be around or talk to Conrad as Clarence Gilyard Jr. is a Capricorn.
When Michelle walks into the office to check the phone records, the door she walks into has a sign that says accountin. No G. Somebody must've been in a hurry. :-)
At 16:45 in the second half (watching the syndicated version) Matlock walks to his car after meeting with the psychologist. As two goons walk by, ostensibly to intimidate him, Matlock goes to unlock the driver's door on his Crown Vic - while the cross-car shot clearly shows the passenger's side front window rolled down all the way.