An Adam Sandler comedy might not be the first thing you’d think would come to mind during a legal thriller like Law Abiding Citizen. But it’s hard to resist paraphrasing the soliloquy delivered in the climax of Billy Madison.

What you’re watching is one of the most insanely idiotic things you have ever seen. At no point in this rambling, incoherent film are screenwriter Kurt Wimmer, director F. Gary Gray or co-stars Jamie Foxx and Gerard Butler even close to anything that could be considered a rational thought. Everyone in the theater is now dumber for having seen it. I award it a half-star, and may God have mercy on its soul.

Law Abiding Citizen is dumb sludge masquerading as rage against the machine – here the flaws in America’s legal system. So depressingly desperate to be a superhero-free Dark Knight is the film that it locks down the city of Philadelphia for a criminal who’s targeting a small group of government officials. There is no Joker in Law Abiding Citizen, but director F. Gary Gray’s film is a flagrantly stupid joke.

Nor is there brotherly love in the film’s lurid opening sequence – a home invasion and the rape and murder of the wife and daughter of Clyde Shelton (Gerard Butler, recently of Gamer and here resembling a doughy Brett Spiner).

Although Clyde is willing to testify, he’s an “unreliable” witness because he blacked out during the attack. It’s either take a plea to get one suspect or go to trial and risk none.

Before Clyde can even choose, ambitious assistant district attorney Nick Rice (Jamie Foxx) brokers that plea. Unwilling to risk his near-perfect conviction rate, Rice takes the plea and, as rankled as he is by the decision, rolls forward in his lawyerly career.

Ten years pass … and no one has aged. Moreover, Clyde has studied each Saw movie and Murder By Numbers so carefully as to plan ultimate moralistic revenge packed with gore and legal loopholes through which he can escape. First, he sabotages the death chamber housing one perpetrator. Then, he gleefully dismembers the other.

Clyde is arrested on suspicion of both murders, but that’s just the start. He wants to bring the whole system down – toying with Rice while targeting the lawyers, judges and detectives who failed him. But how is Clyde doing this from prison? (Yes, prison, not jail – where real-world suspects usually await trial.) Is there an accomplice? You won’t believe the answer … if you’ve ever possessed a single complex thought.

Gray draws up some nifty car explosions, but he made a more exciting, thoughtful and better-acted system-challenging movie 11 years ago with The Negotiator. Hell, if you want something similarly exploitative, it was done far better in 1991’s Ricochet.

Where Denzel Washington and John Lithgow slummed and loved it, Foxx and Butler grimly plow through with straight faces amid mounting absurdity and blathering banter about pommes frites, Peruvian puffer fish and prison-bunk bedding. (Butler produced this dreck, meaning he shares a stronger blame for its lack of structure.)

Meanwhile, Clyde picks off his prey in order of character-actor stature, although he can’t set his sights on the simpering Leslie Bibb soon enough. In one particularly embarrassing scene, Bibb limply whines her way through a crisis of conscience.

That passes for “commentary” in Kurt Wimmer’s script – which combines his crappy cop movies (Street Kings) and moody, wintry dramas where everyone wears overcoats (The Recruit). Also unable to be bothered to correctly write the title as Law-Abiding Citizen, Wimmer merely piles up the inanity of Clyde’s plot in each reel.

Why isn’t there a constant guard on Clyde once he’s dubbed some sort of bin Laden-esque terror suspect? Are we to believe Clyde’s masterstroke could have gone unnoticed for 10 years, or seemingly everyone involved would have forgotten such a horrible case in the first place? Would Clyde’s face not be plastered everywhere so that someone might recognize him? Did Clyde really know the Deftones’ “Engine Number 9” would conveniently blare from his iPod when he shivved that guy?

Brooding masterminds seeking vengeance can take one lesson from Law Abiding Citizen: Booby-trap everything from toilet handles to teacups because you never know when your ludicrously calculated 10-year plan will unravel in just 10 seconds.

Humorless and helpless as it is, there is a better film suggested within Law Abiding Citizen. At one point, Foxx suggests that Butler become sexually active with himself and his potatoes. That one idea is more inspired than anything else in the movie.