Granted, the only really good new release by octogenarian director Sidney Lumet is the two-disc DVD of 1975’s Dog Day Afternoon (Warner, $26.98). This new feature, also a fact-based crime drama, is drab and monotonous by comparison, and star Vin Diesel, relentlessly present in almost every scene, is not the second coming of Al Pacino.

But Diesel is startlingly not bad as Giacomo “Jackie Dee” DiNorscio, the Lucchese family mafioso tried alongside 19 pasta-gobbling goombahs in New Jersey during 1987–88, the longest criminal trial in American history. His only action scenes are the grabby opener, wherein a junkie cousin shoots Jackie (who protests, “But I love you!”) and the rote cocaine sting that earned him a 30-year sentence. When the prosecutor (feisty Sean Kierney) offers to shorten that stint for squealing on the other Luccheses, Jackie indignantly demurs. With nothing to lose, he sacks his lawyer and defends himself in an outrageously farcical way.

The dialogue is said to be taken mostly straight from court transcripts, and it’s ruder than any routine David E. Kelley ever wrote. “I’m not a gangster,” Jackie jives the jury. “I’m a gagster!” Diesel is pretty funny. It’s plausible that this charm would sway jurors. He even gets one scene where he skillfully discredits an expert witness whose testimony looked like a slam dunk against him. Mostly, though, Jackie just blurts out what he thinks, to the constant consternation of the long-suffering judge (Ron Silver) and the no-nonsense gangster defense attorney (Peter Dinklage, showing The Station Agent was no fluke).

Only problem: There’s no story shape to the trial, just a parade of interchangeable thugs. It takes forever for the implausibly saintly Jackie to realize that his Lucchese crime boss (the marvelously malign Alex Rocco) is a prick, like we knew all along. And the testimony, even if real, doesn’t have screenplay rhythms and goal-directedness. When Annabella Sciorra appears as Jackie’s pissed-off yet devoted ex-wife in a rare scene out of court, it’s a wonderful jolt of energy. Then we go back to the aimless one-man stand-up comedy show in the courtroom, badda-bing, badda-boring.

In this post-Sopranos epoch, the gangster genre is a tea bag dipped one time too many. Find Me Guilty brews up nothing new—except for an eyebrow-raisingly competent performance by an actor who can’t get a fair trial in the court of public opinion.