Plot hole: Matlock figures out that The Professor wouldn't have been able to see the security guard from 50 yards without glasses, and that's what tips him off about The Conspiracy: the guard testifying that the man wasn't wearing any. However, when we see the scene happen at the beginning of the episode, the person posing as Prof. Erskine Tate is, in fact, wearing glasses. (00:04:15 - 00:22:15)
Plot hole: The forensics for this case have been quite shoddy at best, considering that Tate was drugged and not simply intoxicated (yet no toxicology test was performed) and the dog wasn't run over but repeatedly beaten with a tyre iron (which is a wildly different kind of injury). Nobody brings this sort of objection forward - the dog one would have easily destroyed the prosecution's case right away since The Professor was asleep at the wheel and not in shape to beat assault dogs up.
Continuity mistake: When Billings offers Prof. Erskine Tate a nightcap, the confetti on his shoulder changes position and quantity in the close-up on Daniel Davis. (00:03:15)
Continuity mistake: When Professor Tate congratulates Eric Lane for the improved grades, the two have a playful banter, and Tate says he's "happy to be proven wrong." Christopher McDonald has to wipe off some streamers that got in his hair. In the next close-up, he still has streamers on his shoulder despite the fact he brushed them away entirely. A similar mistake happens later on when he is carrying the unconscious professor out of the room; streamers suddenly are all over him from one shot to the next. (00:02:40)
Factual error: This takes place in Atlanta, but in the scene where Tyler pulls up to Matlock and The Professor on the bench, there are California-style palm trees visible in the background. (00:18:35)
Answer: If it was ever found out that she was at Terry's house before he was killed, there's a possibility that a lot of people would have begun to suspect her of murdering Terry. By claiming that she wasn't, she was hoping that people wouldn't accuse her of the murder.