It’s easy to understand why Denzel Washington jumped at the chance to play a charismatic, fast-talking, lip-smacking villain in “Training Day.” Not only is his role as a venal, corrupt Los Angeles cop a flashy, flamboyant star turn, but it must have been a welcome change of pace from all the goody two-shoes and righteous martyrs he’s been portraying over the last decade; he was in grave danger of becoming the new Sidney Poitier. And there’s no denying that Washington is up to the challenge: his Detective Sergeant Alonzo Harris, narcotics officer extraordinaire, is certainly an eye-catching, ear-grabbing creation as he drives about the mean streets, spewing orders and doing dirt.

That doesn’t mean, unfortunately, that the cinematic vehicle the star’s ensconced in is a new, or attractive, model. In fact, the screenplay for “Training Day,” by David Ayer, is a pretty broken-down affair, filled with cliches (buffed up, to be sure, but still awfully hoary) and ultimately doomed by a several bursts of idiocy toward the close that wreck it–exactly what you might expect of the man who previously gave us “U-571” and “The Fast and the Furious.” Ayer’s script provides Washington with some succulent lines to munch on and spew out, but in terms of plot it’s extremely messy and, in the third act, positively absurd. And certainly Antoine Fuqua isn’t the man to transform the material into something better than it is. Known for his commercials and music videos, the director brings the same kinetic rush to the picture that he used in his earlier features “The Replacement Killers” and “Bait,” but the emphasis on style over substance ultimately proves more wearying than exhilarating, and since there’s an essential sameness to the cinematic tricks he employs, they become tiresome and predictable long before the two-hour mark is reached. Rather than concealing the screenplay’s weaknesses, Fuqua’s technique merely throws them into greater relief.

The narrative of “Training Day” unfolds over the space of less than twenty-four hours. Naive, wide-eyed (through suitably bedraggled) police rookie Jake Hoyt (Ethan Hawke) is excited by the prospect of working undercover with the legendary Detective Harris and moving up the promotion ladder by succeeding in his elite narcotics unit, but Harris quickly makes it clear that the kid’s on trial: Hoyt’s got to prove his ability and loyalty quickly in order to keep his spot on the squad. It soon becomes clear, however, that in doing so the younger man will have to compromise his principles and sully his hands in shady doings. Within a matter of hours Harris has implicated the hapless trainee in his own Machiavellian machinations, the ultimate purpose of which isn’t made clear until fairly late in the picture, during a mid-afternoon restaurant meeting between Harris and some equally corrupt departmental higher-ups. From this point the plot spins out of control: to secure funds he needs before the day is out, Harris involves Hoyt in the murder and robbery of a drug dealer (Scott Glenn) whom he’d earlier introduced as a buddy, and then he takes the younger man to the forbidding headquarters of a brutal Hispanic gang. It wouldn’t be fair to reveal too much about what happens next (particularly since the reasons behind things get awfully unclear): suffice it to say that the final act is predicated on a coincidence so palpably ridiculous that one can only groan in disbelief at the contrivance. There then ensues a final confrontation that’s bloody awful in every sense, followed by a laughable moment of gangsta nobility that’s obviously been concocted to pander to a sizeable portion of the urban audience, and capped by a shoot-out that trashes the memory of “Bonnie and Clyde.” The picture has been careening downhill from fairly early in the running-time, but during the last half-hour it goes completely off track.

Throughout the debacle Washington exudes energy, but after initially impressing us, his essentially one-note turn–extravagantly high-pitched as it is–comes to seem a pointless bit of exhibitionism, more a stunt than a performance. By contrast, Hawke is a complete wallflower. His character is at first in awe of Harris, of course, so the actor’s initial diffidence is appropriate; but by the end Hoyt is supposed to have developed into a convincing opponent to the older man, and Hawke proves entirely inadequate to the challenge, remaining a feeble rival who could be slapped aside by a guy like Harris without breaking a sweat. There are other people in the cast, of course, but the movie is basically a two-man show; Glenn, for instance, uses his now-wizened face to good effect, but he’s otherwise a sleepy presence, and even such recognizable figures as Tom Berenger and Snoop Dogg make very little impression. (The seemingly ubiquitous Harris Yulin does stand out, but not to good effect.)

One of the most notable things about “Training Day” is the negligible attention given to women in it. Hoyt has a wife who sends him off hopefully at the beginning of the story, but she disappears after that; Harris has a wife too (at least I think she’s his wife), but he treats her as though she were little better than a hooker (while virtually ignoring the angelic little son he has by her). The only other female of consequence is a young Latina who cuts school and winds up nearly raped. From this is should be clear that Fuqua’s picture is basically a macho exercise, one of those pieces focusing on a face-off between a colorful bully and a Walter Mitty type in which the worm finally turns. It’s an old formula, but one that still has life in it. Unfortunately, though Washington tries hard– maybe too hard–to make his part of the equation work, the preposterously convoluted story he’s saddled with undermines his efforts; and Hawke proves completely incapable of holding up his side of things. By the time its drawn-out finale lurches to a screeching close, “Training Day” has come to feel more like “The Longest Day.”