There are enough holes in the legal minutia of "Runaway Jury" to keep anyone with a law degree laughing from beginning to end. But for the rest of us, this fast-paced thriller's twist-crescendo-ing plot and sharp performances should at least delay the feeling of being duped until after the credits roll.

Another popcorny courtroom concoction from a John Grisham novel, the movie is a sensationalized peek into jury tampering during a big-money wrongful-death suit filed against an assault-weapon manufacturer after a workplace shooting.

The film wears its politics on its sleeve: the rich, cigar-smoking, unrepentant gun industry honchos have hired an unscrupulous jury consultant (deliciously iniquitous Gene Hackman) with the high-tech means to dig up dirt and create graphic-intensive computer-screen portfolios on everybody who received a jury summons for the case.

Bent on manipulating every aspect of the trial, Hackman employs hidden cameras and bugs to spy on potential jurors, and radio ear-pieces to coach gun company lawyers through their questioning. Meanwhile, the plaintiff -- a pretty young widow (Joanna Going) whose husband (Dylan McDermott) was one of nine people killed by a disgruntled co-worker -- is represented by the more affordable, far more principled, vaguely scatty but not-as-provincial-as-he-seems Dustin Hoffman.

But what neither of these camps knows is that the jury they eventually choose will include a wildcard with designs on manipulating them. John Cusack plays a videogame store clerk with no traceable background, whom Hackman reluctantly approves in a tight pinch during jury selection -- and soon the outwardly laid-back guy reveals an elusive, dodgy personal agenda, not to his fellow jurors, but to the lawyers. For $10 million, he reveals through a liaison, he'll swing the jury in favor of whichever party pays him off.

Can he really guarantee a verdict? The lawyers don't know, but Cusack demonstrates what looks to them like astonishing influence -- even getting one panelist removed, then getting the rest sequestered just to prove his behind-the-scenes sway. Is he really for sale or is there an ulterior motive at work here, cooked by Cusack and his tenacious girlfriend (Rachel Weisz), who stage-manages her own scoreboard of juror's profiles?

Director Gary Fleder ("Don't Say a Word") does a clumsy dance around this larger question for the bulk of the picture, as Cusack and Weisz talk about everything but their intentions. She tries to play Hoffman, who refuses her demands on principle (before thinking twice later on), against the more menacing Hackman, who resorts to ordering Cusack's gritty New Orleans flat burglarized (looking for blackmail evidence) and burned down (for intimidation). But since neither lawyer, or our conspirators, wants a mistrial, the case goes on through it all.

At times "Runaway Jury" seems headed toward a runaway credibility problem, but Fleder deftly keeps the tension so tightly wound and the multilayered narrative so swift and taut that its many, mostly minor dubious conceits don't have time to add up. Other times the movie threatens to degenerate into a standard-issue courtroom drama, with a gun company executive blowing up on the stand in "You can't handle the truth!" style and cheaply symbolic slow-motion shots of blind-justice statues.

It's clear early on that Fleder is worried jury selection and later deliberation won't seem sexy enough -- even with all this intrigue -- so he punches up such scenes with freeze frames and acute edits, a score of thundering drums, and data flashing across 46-inch flat-panel computer screens in Hackman's clandestine headquarters. Meanwhile, he settles for pretty generic New Orleans ambiance (insert passing Cajun-voodoo reference here).

The director also has more talent employed than he knows what to do with. Engrossing in their moral ambiguity, Cusack, Weisz and Hackman get 90 percent of the screen time -- which is appropriate given that they're the central characters. But Hoffman doesn't have much to sink his teeth into, and a great supporting cast (Cliff Curtis, Luis Guzman, Jennifer Beals, Jeremy Piven) have minor roles at best, single lines of dialogue at worst.

The longer the movie goes on, the more implausible, deliberate and hot-button moralizing it becomes (there are even quite a few pot-shots taken at the cigarette industry, which served as defendant in the Grisham's novel). But Fleder never lets the riveting, dense tension go slack, and as secrets are revealed it builds to a satisfying climax.

Great drama, it ain't. But as a bracing matinee thriller "Runaway Jury" delivers.