Actor Michael B. Jordan, who portrays Grant, has seen it all before. "I'm from Newark, New Jersey, and I used to catch the train all the time from Newark to Manhattan when I was going to auditions, growing up," he says. "And during the holidays, it was the same: me and my friends would go to the city to hang out, and you'd see altercations with police officers and passengers all the time. It didn't escalate to that level but … me and Oscar are very close in age, so it could've easily been me."

Moreover, arrived in the wake of last year's controversial acquittal by a Florida jury of former neighbourhood watch captain George Zimmerman of manslaughter and second-degree murder in the fatal shooting of Trayvon Martin, a 17-year-old African-American. The verdict led protesters to take to the streets in more than 100 American cities, with ugly riots in Los Angeles.

Factor in the deaths of Amadou Diallo, unarmed and shot dead by four NYPD plainclothes officers in 1999, and Sean Bell, gunned down in Queens on the eve of his wedding in 2006, and Grant's death is hardly an isolated incident. The police officers involved in those two deaths were acquitted.

"There's a theme that's happening right now with young men and police brutality," says Melonie Diaz, who plays Sophina, Grant's girlfriend and the mother of his young daughter. "I think it happens all the time and sometimes we don't even know about it, which is even scarier," the 29-year-old actress says.

But what makes Grant's death almost unique is that several bystanders recorded the incident on mobile phone cameras, posting footage on YouTube that was subsequently used in 's terrifying opening.

"It had a very different impact than if it'd happened in the dark and if it was just the police officer's word against the witnesses' word," says Coogler. "You look at the Sean Bell case or the Trayvon Martin case - there's no video there. It's just the word of a guy who is alive now against a guy who is dead."

That Coogler was raised in Oakland, not far from where Grant lived, helped him get access to Grant's family. "They trusted him because he's from the same neighbourhood," says Jordan. "They knew his angle. He's a resident, a very proud Bay Area resident, and they trusted him with Oscar's legacy and his life."

The fact that the 27-year-old Jordan starred in TV show , playing the drug-dealing Wallace, also helped. "They were all fans of , so it was a little easier [for them] to open up to me," he says.

While Coogler grew up close to where Grant lived, he was one of the lucky ones: his parents scraped together enough money to privately educate him. After studying at the University of Southern California's film school, he worked as a youth guidance counsellor, but when he heard Grant's story he felt it deserved to be retold on film. Developing his idea through the Sundance Screenwriters Lab, the first-time director managed to find support from Hollywood star Forest Whitaker.

The veteran actor was immediately taken by Coogler's vision, backing the film through his outfit Significant Productions. "I felt he was going to put a human face on an issue that would deepen our understanding of this situation," Whitaker says.

Support also came from Octavia Spencer. Cast as Grant's mother, Wanda, the actress who had just won an Oscar for served as an executive producer, helping to find money when financing fell through.

"She was like an Energizer battery on set for everybody," Coogler says, smiling. "We couldn't have done this without her."

Inevitably, in dealing with such an incendiary topic, the film has led to divided reactions. At Sundance last year, where movie mogul Harvey Weinstein paid US$2 million for the US distribution rights, it won the Grand Jury Prize and the Audience Award, only the fourth film in the history of the festival to do so. It claimed the Avenir Prize in the Un Certain Regard section in Cannes, and best first feature at the Independent Spirit Awards.

However, it did not score any Academy Award nominations and there have been criticisms too. "I know there are people out there who have problems with the film," Coogler says, shrugging.

Many of the issues concern his depiction of Grant. A small-time criminal who cheated on his girlfriend and was fired from his job at a grocery store, Grant was no saint. Yet, to quote magazine, the film "tries to fit a halo on its subject", including scenes of Grant nursing an injured pit-bull dog he finds lying in the road and throwing away a bag of marijuana, vowing to give up his petty drug-dealing.

Spencer jumps to her director's defence: "Ryan presented this young man warts and all." And there's some truth to this, with Coogler pointing out the flashbacks he inserted. "We see him in prison saying horrible things to his mom, threatening other people, and getting into an altercation with the guards and resisting their restraint. I don't think any of those things are saintly at all." What's more, Grant's mother had no idea he was still dealing drugs. "That's very rough for his family to learn and find out and watch."

Coogler says he approached his research scrupulously, initially studying public records and trial documents. Later, a friend working as a civil attorney for Grant's family allowed him access to witness testimonies from people on the train and further court transcripts. "Every single choice that I made was based on research, and based on things people told me about Oscar, because I didn't want to … invent this character out of thin air," the director says.

Jordan says Grant was "polarised" in the media. "He was either depicted as a monster - this horrible human being - or as a complete saint," he says.

"And he's being judged by people who don't know him - so the best thing me and Ryan could do was to get to know him through the people who knew him best - his daughter, his mom, the people that really cared about him, that really knew him. We just let him be a flawed human being, as we all are."

Fruitvale Station