It’s not merely the presence of (an uncredited) Dylan McDermott that makes this screen adaptation of John Grisham’s legal thriller play like a glorified episode of “The Practice.” He disappears after just a few minutes of “Runaway Jury”–the victim of a shooting that leads to the central case against a gun manufacturer–but the rest of the picture reflects the overwrought us-vs.-them mentality, melodramatic consideration of ethical dilemmas and glossy style characteristic of the David Kelley courtroom drama in which he used to star.

Ultimately, though, Gary Fleder’s film comes across as even less plausible as the television program. “The Practice” has had its share of convoluted, Machiavellian schemes, one-dimensional characters and unlikely plot turns, but they seem positively modest beside what one finds here. The premise of the tale is that the wife of McDermott’s character brings civil suit against the manufacturer of the firearm that killed him, charging willful negligence that carries responsibility for his death; the case, which could result in a landmark finding against a gun firm, is taken up by activist attorney Wendall Rohr, played by Dustin Hoffman in his best rumpled, principled style. If the verdict favors the plaintiff, it will serve as a precedent and lead to a landslide of claims that would cripple the industry; and so the manufacturers band together to hire not only a first-rate defense team headed by slick Durwood Cable (Bruce Davison), but even more importantly the most notorious of all jury consultants, the dictatorial, amoral but canny Rankin Fitch (Gene Hackman). Hackman arrives in New Orleans, where the trial is to be held, like a martinet general, presiding over a warehouse full of computer screens and underlings and barking orders to the defense counsel via a secret communications device. We watch the jury assembled–the typical motley crew–and clearly the most important of them is Nick Easter (John Cusack), a computer-game salesman so eager not to serve that he irritates the judge. But wouldn’t you know, Nick turns out to be a master manipulator who, together with his outside contact Marlee (Rachel Weisz), offers to turn the verdict in either direction, depending on which side is willing to pay them a whole bunch of money. The furious Fitch acts to identify the inside person and track down Marlee while Rohr has a crisis of conscience about whether to bid for a victory or be true to his legal ideals.

It wouldn’t be fair to reveal the twists and turns that the jury-tampering scenario takes, other than to say they involve Grisham’s customary chases and near-escapes and a big surprise at the close. What is fair is to characterize the goings-on as not merely implausible but so far-fetched as to positively prohibit a suspension of disbelief. Even the lead characters are all mere sketches rather than rounded personalities, and while the performers all bring their strengths to the table–Cusack his boyish charm, Hackman his belligerent power, Hoffman his downtrodden caginess and Weisz her slinky sultriness–none can invest them with any depth. As for the other jurors, the collection of stereotypes–the gruff marine (Cliff Curtis), the lady drunkard (Nora Dunn), even, if you can believe it, a blind man (Gerry Bamman) to show all too bluntly the true naturenof justice, among others–is even more obviously drawn from the pulp writer’s handbook; they make “Twelve Angry Men” look unbelievably sophisticated by comparison. Davison, Bruce McGill (as the ornery judge) and Jeremy Piven (as Rohr’s dedicated jury consultant) are stuck trying to breathe life into stock figures, too.

But shallowness is perhaps to be expected in a Grisham story. What’s beyond the pale here is that “Runaway Jury,” even more than “The Practice,” inhabits a legal fantasy land that’s impossible to swallow. The basic presumption that one could arrange his service as a juror on a particular case is difficult enough, but much added unlikelihood follows. Yes, jury consultants are important, but the notion that they march around like military establishments and engage in burglary, arson and even murder stretches credulity, as also does the notion that witnesses can be made suddenly to disappear, or that manifest jury tampering would not be reported to the court, or even that one juror could so easily manipulate the others. It may be amusing to watch Cusack twist everybody–including the judge–around his little finger, but one never believes for an instant that it could happen. Simply put, this is no competition for “The Insider,” a much truer and more credible film (and one that involved a tobacco case, just as Grisham’s book originally did).

Still, “Runaway Jury” is efficiently made, its powerhouse cast delivers the simpleminded goods, and it has a crowd-pleasing denouement that embodies Oscar Wilde’s definition of fiction–the good end happily, and the bad unhappily. If an expert presentation is enough for you to forgive the utter absurdity of the melodramatic plot, assume your seat in the courtroom; otherwise, take the usual evasive measures to avoid jury duty.