The movie star reveals he had hoped to speak to Bulger in person as part of his research for the film, which was adapted from DICk Lehr and Gerry O'Neill's bestselling 2001 book Black Mass: The True Story Of An Unholy Alliance Between The FBI And The Irish Mob, but the Boston crime boss was not interested.

Speaking to reporters at the Venice Film Festival in Italy on Friday (04Sep15), Depp admitted, "I don't believe he was a great fan of the book (the film is based on)."

However, Depp was able to get the thumbs up for his performance from one of Bulger's close associates after his attorney, J.W. Carney, Jr., stopped by the set of director Scott Cooper's crime drama twice during filming.

The actor claims Carney, Jr. was impressed with the accuracy of Depp's portrayal, adding, "(He) said he could feel his old friend in what I was doing."

Discussing his character, Depp continued, "With a character like James Bulger, I think you have to approach him just as a human being. Nobody wakes up in the morning and shaves or brushes their teeth and looks in the mirror and thinks, 'I'm evil.'

"He was complicated... He would take in little old ladies' groceries into the house, and then 10 minutes later he might be bashing someone's skull in."

Bulger, now 86, went on the run from authorities in 1995 and became one of America's most-wanted fugitives. He was finally captured 16 years later in California in 2011, and is currently serving life in prison after he was indicted for 19 murders.

Black Mass received raved reviews from critics when it was screened in Venice on Friday morning, ahead of its evening premiere, with reporters tipping Depp as an early contender for the Best Actor Oscar at next year's (16) ceremony.