The Stripper - S1-E3
Stupidity: The whole plot resolution can happen merely because, on top of Matlock's unbelievable guess on how to trigger someone's dormant personality - apparently murder wasn't enough, but a joke is - the transvestite has two entirely separate voices, one of which is a dubbed-in female one. Not quite believable even for the times.
Stupidity: The gas station attendant can (at least hypothetically, he turns out to be wrong) recognise someone who did a hit-and-run a long distance away at night, but somehow he does not recognise in court the client of the station who was with him at the same time and interacted with him for a few minutes.
Stupidity: As far-fetched as Matlock's stunts can be in most episodes, in this one you have one of the most egregious examples of something that would never stand. Here, The Witness confesses to murder under the direct threat of an attack dog that Matlock practically sic[s] on him, and nobody bats an eyelid about it. On top of that, the culprit and his associates are all legal scholars, as the episode itself more than once reminds the viewer.
Stupidity: Amazing how people on this show, like The Accused here and in the earlier episode "The Chef", are leaving their doors unlocked or no explanations given as to how the actual killer planted the evidence.
Answer: I did not see this episode, but YES. Both prosecution and defense lawyers use investigators to search for and uncover evidence that is legally admissible.