OJ Simpson's 'prison BFF' describes Simpson's life in prison

— -- The hit TV show "The People v. O.J. Simpson: American Crime Story" portrays O.J. Simpson as cocky and confident.

Now another image of the former NFL star, nicknamed "The Juice," shows Simpson as a locked-up inmate who is battling weight gain and arthritis but still living a life of relative privilege -- for an inmate.

"O.J. Simpson is not suffering in prison," retired correctional officer Jeffrey Felix told ABC News. "He's eating well. He's exercising well. He's got a flat screen TV."

Felix is the author of a new, tell-all book titled, "Guarding the Juice: How O.J. Simpson became my Prison BFF." In the self-published book, Felix said that for seven years, he was Simpson's closest confidant at Nevada's Lovelock Correctional Center, where O.J. is serving a 33-year sentence for kidnapping and robbery.

"He thinks that Nevada's making up for California and that because California couldn't convict him for the murders, that they convicted him on some B.S. charges -- as O.J. would say," Felix said.

Infamous for beating murder charges in the 1994 deaths of his ex-wife, Nicole Brown Simpson, and her friend Ron Goldman, Simpson argued at a 2013 parole board ruling that he has been a model prisoner. He is up for parole next year.

Simpson was found not guilty of the murders in a 1995 criminal trial. He was found liable for the two deaths in a subsequent civil suit brought by the families of Brown Simpson and Goldman.

The trial of Simpson for murders of Brown Simpson and Goldman is portrayed in "American Crime Story," with Oscar winner Cuba Gooding Jr. portraying Simpson.

Felix said that even though he has not seen Simpson since he retired last September, he heard from a contact inside the prison how Simpson reacted to recent news of a knife found at his former California estate that investigators are now examining.

"O.J. thinks the knife thing is a complete joke and he wants to know why it was held on to for 18 years before it was turned in," Felix said. "He jokingly says, 'If the knife is rusted, I can't be busted.'"

Felix said he believes Simpson is guilty of the murders of Brown Simpson and Goldman.

"O.J. told me one time that only two people alive know who committed the Brentwood murders: him and Al Cowlings," Felix recalled. "Al Cowlings was the one that drove the white Bronco and Al Cowlings was O.J.'s best friend."

"When O.J. was washing his hands and looked in the mirror, I said, 'Juice, you just solved the Brentwood murders. You're looking at the murderer right in, in the mirror,'" Felix said. "And he just gave me a glare."

"He gave me kind of a dirty look and then he kind of smiled afterwards," Felix said. "He kind of shrugged it off a little bit."

One of the attorneys who represented Simpson in the 1995 trial was Robert Kardashian. According to Felix, Simpson claimed that Kardashian’s daughters -- Khloe and Kim Kardashian -- and Kim’s husband, Kanye West, called and wrote to Simpson behind bars. A representative for West and Kim Kardashian denied the claim.

Update: On July 20, 2017, Simpson's attorney, Malcolm LaVergne, cast doubt on Felix's account, telling reporters after the former football player was granted parole that Felix's book included false information.