Warning: Wikipedia contains spoilers
After appearing before the judge at the arraignment in his nephew's murder case in a leather jacket without a tie Vinny is thrown into jail for failing to enter a plea of "not guilty" for his nephew and friend and for not giving the judge due respect. On his second appearance before the same judge Vinny Gambini does not even bother to cross examine one witness in the probable cause hearing. His nephew and his friend decide to hire the public defender but they quickly realize that Cousin Vinny (who failed the bar exam five times before passing) is still a superior lawyer than available through local legal aid.
Vinny's brilliant style comes to the fore during the trial when his cross-examination techniques expose the weaknesses in the prosecutor's case. Of course his brilliant denouement would not have been possible without his fiancée's ability to serve as an expert witness. None the less Vinny's performance and his tribulations are an exemplary presentation of the skill necessary for a criminal defense trial lawyer to succeed at trial and why so many lawyer plead their cases out and accept a plea bargain or settlement when faced with the vagaries of courtroom practice.