Biggie Smalls was murdered 12 years ago. Now Jamal Woolard's portrayal of the rapper in Notorious is bringing pain among the plaudits, such is his uncanny likeness to him

He wondered why Biggie never took his sunglasses off, and did some stuff he didndidn't quite understand the meaning of at first – crawling around on the floor like a cat, rapping while gripping his

tongue.

When he arrived at the Notorious set, his likeness to Biggie was uncanny, and unnerving. "The first time I went on set and saw him rehearse, I walked out," says the rapper Lil' Cease, Biggie's close friend. "It took a while to get used to."

When we meet at Frank White, a Brooklyn caf named after one of Biggie's alter egos, Woolard, also known as the rapper Gravy, has his own explanation for the silence, gasps and tears he faced during his transformation into Biggie. "Some people couldn't stomach it," he says. "Puff (Sean Combs, who owns Bad Boy Records, Biggie's record label] couldn't stay around. He just couldn't take it. But I felt like that's my job. They were hurting, but I'm not here to hurt you, I'm here to give you what you want." And also what a film like Notorious absolutely demands: an eerily credible re-creation of its protagonist. "If Biggie doesn't work, the movie doesn't work," says the film's director, George Tillman Jr. This week audiences and critics will get to decide if the efforts of Woolard and his many coaches have paid off, which would be a particularly impressive accomplishment given that the real Biggie Smalls, born Christopher Wallace, died only 12 years ago – murdered in March 1997 in Los Angeles in a still unsolved drive-by shooting – and remains fresh in the minds of many.

Woolard, 33, did not take his opportunity lightly. "A responsibility," he calls it. Though Biggie's career was brief – he was 24 when he was killed, less than two weeks before his second album was released – he remains one of rap's seminal figures, lauded for bringing emotional complexity to street life, for his improbable sex appeal (Biggie stood 6ft 3in and weighed well over 300lb) and for his syrupy, intricate rhyme schemes.

Woolard, who had no previous acting experience, went to his audition in character: Coogi sweater, wide black sunglasses, Kangol hat just so. For the first few weeks of his training routine – "Biggie boot camp" it was called – he worked without pay; he still didn't formally have the role. "It was a good psychological trick," he says. "Any day they could have said, 'Never mind'." Every day he met with one or more of his advisers: Mimi Lieber, an acting coach; Kate Wilson, a vocal coach; Tanisha Scott, a choreographer; and several other informal teachers who lived the events depicted in the film: Lil' Cease; Biggie's hype man, Money L; the music producer Deric (D-Dot) Angelettie; and Biggie's mother, Voletta Wallace.

"I felt like I sometimes intimidated him during the film," Wallace says. "I felt bad for that, but as a producer my job is to be there," which she was throughout filming, except for the scenes in Los Angeles leading up to her son's murder. ("She took a lot of tears," Woolard said of Wallace's time on the set, "but that one was too much").

Woolard shares many characteristics with the man he was trying to embody – portly and amiable Brooklyn rappers both. He grew up just a few blocks from Biggie's childhood home on St James Place near the border of Fort Greene and Bedford-Stuyvesant. Both men dealt drugs as teenagers, though Woolard describes his family situation as having been more dire than Biggie's. Woolard's mother struggled with drugs, he said, and his father, with whom he had never been close, died of Aids. "Ms Wallace would call him every day for dinner," he says of the young Biggie. "I ain't have dinner. I would have appreciated to have his life."

Woolard tapped into his own history to help him understand Biggie's inner struggles. "He went to places he never imagined internally, places that were quite dark," Lieber says. In preparing for a scene in which Biggie tells a friend that his own mother has cancer, Lieber asked Woolard to summon his relationship with his mother.

"He started to cry," she recalls of the session. "He felt very difficult feelings for the first time, and he didn't know what to do with them. He kept wanting to be Jamal, saying, 'I don't like this, I don't want to do this.' But he stayed with it, which is an act of huge courage."

Sandpapering down his rap habits as Gravy proved a different kind of challenge. "Biggie's vocal pattern, that's a hard flow to get," Tillman says. "He realised, 'I can't do the Gravy flow. I have to get out of that.'"

Scott, the choreographer, helped Woolard tone down his hyper performance style as Gravy. "Biggie was very cool with his moves, laid back and suave," she says. "Jamal danced less but moved around more, so we changed that." Woolard also sweated the small stuff. He knew Voletta Wallace listened to country music in the house when Biggie was growing up, so he bought a Willie Nelson album and subjected himself to it. ("Corny music, that's what I felt.") Lil' Cease told him Biggie always carried an asthma inhaler, so he got a hold of one, just in case. To perfect Biggie's signature wobble he studied the Penguin from the Batman movies.

Biggie's murder, along with the killing of Tupac Shakur six months earlier (results, some believe, of a feud between the rap worlds of New York and Los Angeles), left scars in hip-hop that are only just beginning to fade. But in the years since, gunshots have become dismayingly commonplace in rap.

Woolard himself was shot in 2006 outside the studios of the New York hip-hop radio station Hot 97, sustaining a minor injury. He proceeded to do a scheduled interview there, and some thought that the incident had been staged, a relative unknown's ham-handed attempt to gain street cachet. He isn't inclined to talk about the shooting, but whatever the case, it unravelled any career and stability Woolard had secured to that point, resulting only in ignominy and stress. Both he and his music were banned from Hot 97. He was dropped from his recording contract with Warner Brothers and fled the city for the South, "to get focused on my life as a man".

"I felt like New York was too much on me at the time," he says. "I was lost. I had a bad situation, everything fell out on me, my wife was pregnant. What was I going to do?"

A friend called him and insisted he come back to New York to audition for Notorious, though it seemed an impossibly long shot. (His audition was separate from the open casting call the studio had held.) His reputation had preceded him, for better and worse.

"I was worried about the vibe a lot of people had on him because of the shooting and the way he might have moved," says Mark Pitts, Biggie's former co-manager and a producer of the film. "I didn't want people not giving B.I.G. his just due because of nervousness about Jamal."

Even now, several months after filming has ended, Woolard is mindful of the walls that need to remain erected between himself as Gravy and himself as an actor inhabiting his role. For the duration of the filming, to avoid dissonance, he stopped writing raps as Gravy, and he hasn't picked up the pen yet. It's as if, even though the cameras have been off for months, he's still in character.

"That's not my calling right now," he says of his original rap alter ego. "At the end of the day it's my job to make sure I nail this. How could I come back to Brooklyn, how could I come back home and be a laughing stock? I live here."

Notorious is released in the UK on 16 January

21 May 1972 Biggie is born Christopher George Latore Wallace in Brooklyn, New York.

13 September 1994 releases his debut album, Ready to Die, on Bad Boy Records.

30 November 1994 Tupac Shakur is shot four times during a robbery in New York City: he loses $40,000 of jewellery and claims that Biggie is in some way involved in the shooting.

1995 Biggie is arrested in Manhattan after attacking fans with a baseball bat.

1995 Releases the single Who Shot Ya, apparently directed at Tupac, below.

1995 Biggie marries singer Faith Evans just nine days after meeting her for the first time.

1996 Tupac releases Hit 'Em Up, a scathing attack on Biggie and other artists on the Bad Boy roster, in which he claims to have slept with Biggie's wife.

9 September 1996 Tupac is wounded in a drive-by shooting in Las Vegas. He dies in hospital five days later.

9 March 1997 Biggie is killed in a drive-by shooting in Los Angeles.

25 March 1997 Just two weeks after his death, Biggie's second album, Life After Death, is released.

7 December 1999 Nearly three years after Biggie's death, Puff Daddy puts out an album of previously unreleased material by Biggie, entitled Born Again.

2002: Release of a feature-length documentary film about Biggie Smalls and Tupac Shakur, made by Nick Broomfield.

16 January 2009 The Biggie Smalls biopic, Notorious, is released in cinemas worldwide.