Continuity mistake: When the Judge asks Vinny if his clients are guilty or not guilty, he does not have his fingers on his cheeks. Then in the next shot of Vinny answering the question, we see the Judge has his fingers on his cheeks. But when the shot goes back to the Judge telling Vinny that he doesn't understand the question, the fingers are not on his cheeks anymore.
Other mistake: When the expert is testifying about the analysis of the tire residue, he says he used a "dual column gas chromatograph with flame analyzation detector." It should have been "flame ionization detector."
Factual error: When Lisa is testifying about the 1963 Pontiac Tempest and the 1964 Buick Skylark being the same height, width, and wheelbase. While the Tempest and Skylark shared the same components, the 1963 and 1964 models were quite different from each other. The 1964 Skylark and Tempest moved to a 115 inch wheelbase and a larger body and frame. The 1963 Skylark and Tempest were smaller with a 112 inch wheelbase. It is hard to believe that someone would confuse a 1963 Pontiac Tempest convertible with a 1964 Buick Skylark as they were completely different cars with a different height, width, and wheelbase.
Continuity mistake: In the scene outside with the judge, after the trial, and he is talking about the fax from NY. Ms Vito put her hand on Vinny's back with red fingernails. As they are driving down the road they are a dull mauve color.
Plot hole: While we never see Lisa leave the courtroom at the end to call Judge Malloy to send the fax verifying Jerry Callo, it is possible she snuck away for a minute to do it after the dismissal and before they leave the town. However, Vinnie does not ever seem to mention that he told the judge he is Callo to her so how did she know? He must have mentioned it to her while they were rushing to leave, they were back on speaking terms and she called Malloy.
Audio problem: After Indy questions the old lady about her glasses, he walks back to the desk and high fives his fiance. Their hands don't touch but still produce a slap.