The former football star is currently serving a prison sentence at a correctional facility in Nevada on charges of armed robbery and kidnapping relating to a sports memorabilia heist in Las Vegas in 2007.

Prison employee Jeffrey Felix became a close confidante of Simpson during his time working at the Lovelock Correctional Center, and he is now detailing their friendship in a book titled Guarding the Juice.

Felix, who retired from his role as a prison guard at the centre in September (15), tells the New York Post, "O.J. picked me out. He ended up trusting me... He said, 'You're like a brother to me'... He's such a nice guy, but, come on, we know he did it."

The footballer-turned-actor was at the centre of a high-profile murder trial in 1995 after he was accused of fatally stabbing his wife Nicole Brown Simpson and her friend Ron Goldman.

The headline-grabbing case ended in a not guilty verdict as Simpson was sensationally acquitted of the charges.