Ethan Hawke joins the NYPD and leaves criminals star-struck

It's a beautiful character," Ethan Hawke enthuses, "who in the first scene commits a murder, and in the second goes to confession and then can't confess. He feels he's got 200 pounds on his shoulders, a giant gorilla on his back, which is that he's failed his wife."

The 39-year-old New Yorker is talking about his latest role in Brooklyn's Finest, a gritty cop drama which reunites Hawke with his director from Training Day, Antoine Fuqua, and co-stars Don Cheadle, Richard Gere and Wesley Snipes. He plays Sal, an under-paid, over-stretched NYPD cop.

To understand his character, Hawke hung out with real cops and went on "ride-arounds", in Patterson, New Jersey. He did the same thing in LA for Training Day, nearly a decade ago. Back then, he says, "None of the cops or criminals were really big on Before Sunset or Before Sunrise." He laughs: "I could be completely anonymous."

But cops really liked Training Day, he says, so this time round he wasn't "just some punk actor in the back seat." When he helped to bust suspects, "they couldn't believe they were getting arrested by the dude from Training Day. They stopped caring they were getting arrested and wanted to get their picture taken."

Gritty and complex, Brooklyn's Finest is the kind of meaty movie that excites Hawke. This is to be expected from someone who, as a child, aspired to become a writer like Jack London. Hawke's interest in acting developed at school, though it was not until his break-through in Dead Poets Society that he decided to pursue it seriously.

Hawke, who lives in Manhattan with his second wife, Ryan Shawhughes – the former nanny of his two children by his first wife, Uma Thurman – and their daughter Clementine, has not given up on writing. He already has two well-received novels under his belt – Ash Wednesday and The Hottest State (which he made into a film in 2006) – and is currently working on a third. His aim was to have three published by the time he was 40; 41 now seems likelier, he says.

Meanwhile, he is continuing to work on projects with his close friend Richard Linklater, who has directed him in several films. He's almost certain that there will be a sequel to Before Sunrise and Before Sunset. "I know Rick and Julie [Delpy] and I will do something else together. We're always emailing each other with ideas."

'Brooklyn's Finest' opens today