If you see just one cop film over the next twelve months, best make it this one.

Training Day is much more than your average cop flick. If Denzel Washington doesn't rate an Oscar mention for his portrayal of veteran drug squad detective Alonzo Harris, there's no justice in this world.

Maybe that's the point. The place, Los Angeles. The time, the present day. It's a city of freeways and gloomy side streets, suburban bungalows masking inner city brutality, a murderous patchwork of ruthless street gangs.

Alonzo (Washington) is a thirteen-year veteran of the force whose work twists logic and justice out of shape. To beat drugs, he has to beat the gangbangers at their own game. He deals in shades of grey, not black and white. Murder, extortion, theft, smoking PCP - the police do them too. And once you've crossed the line once, the rules change for ever.

Idealistic uniform cop Jake Hoyt (Ethan Hawke) wants into the drug squad so he can make a difference and make detective. But first he has to ride with Alonzo for a day to see if he makes the grade.

The action is set over the course of Hoyt's first 24 hours on the job - his training day. Shot on location in wrong-side-of-the-tracks LA neighbourhoods like Crenshaw, Watts and the Jungle, the frames fizz with street energy.

Washington dominates this film. During the few scenes towards the end when he's not on camera, it leaves a gap on screen. Alonzo is a charismatic ball of street smart aggression, ready to flip out at any moment. Washington conveys the internal tension of a man who decided a long time ago that he had to do wrong to do what's right. As the film unfolds, the true extent of his corruption is revealed. But to the end, the murderous, cynical policeman is a kind of fallen hero. "To protect the sheep you need to kill the wolves," he says. "It takes a wolf to catch a wolf."

Opposite a performance like this, Ethan Hawke was in real danger of fading off screen. But still he hangs in there, a stranger slowly learning the rules of a strange land, full of uncertainty, scared for his life. He's a pawn in Harris' game, a partner turned prey who has just one day to pick up the street smarts that will get him through. As Harris tells him: "You have to decide if you want to go to the grave of if you want to go home."

Even the inevitable cameos by rappers - Snoop Dogg as a wheelchair-bound crack dealer and Dr Dre as one of Harris' cold-eyed accomplices - can't detract from this one. Hip hop is mostly play-acting anyway. And singer Macy Gray captures a real sense of nihilistic defiance as the wife of a ghetto drug dealer.

Did we really need the predictable, blaze of gunfire ending? Despite this, Washington's performance makes this one you won't want to miss. The film's chain-reaction, trial-by-ordeal narrative carries a mythological undertow, and Alonzo's inevitable downfall has the feel of classic Greek tragedy. See it.