With macabre timing, the latest of many books on his case will reach the shops in France this week. It contends that contrary to what he has always claimed and what the majority of French have come to believe, the young Tunisian did murder Ghislaine Marchal at her villa near Nice in June 1991.
The truth may never be established for sure. Mr Raddad cannot be tried twice for the same offence. More significantly, the case has drawn attention to the curious fact that, under French law, he was unable to appeal against his criminal conviction, despite an accumulation of evidence that the original court finding in February 1994 was unsafe.
The Omar affair once held France in its grip almost as completely as the OJ Simpson case captivated America and the world. Could the baby-faced gardener, then 29, have brutally stabbed the widow who had always treated him kindly? What of the bizarre inscription found written in blood on the cellar wall, close to the body? Ms Marchal had apparently written with her finger in her own blood: "Omar m'a tuer. Omar m'a t..." ("Omar killed me.")
Given the severity of her injuries, could she really have written this? Would a well-educated woman have made the grammatical error of writing "tuer" instead of "tuee"? Was it her handwriting in any case? These are questions which have drawn conflicting answers from forensic scientists. One expert told the trial it was 99 per cent certain that Ms Marchal had written the words; another expert has since pronounced that she almost certainly did not.
Defence lawyers and campaigners for Mr Raddad's release have always insisted that the message was written by the real murderer to throw suspicion on to the young gardener. The weight of doubt became so great that in 1996 President Jacques Chirac gave him a partial pardon, reducing his sentence from 18 years to four years and eight months.
Adding further to the drama of the Omar affair, Mr Raddad should actually have been freed several months ago, but it was a condition of his parole that he must have a job before leaving prison. He was only released on Friday after the Justice Ministry approved an offer from a Halal butchers chain in Marseilles, which is ready to employ him as a stock-keeper.
Mr Raddad left prison with his lawyer, Jacques Verges, a veteran defender of unpopular causes. Both men vowed to continue the fight to clear his name. But the new book, L'Affaire Omar Raddad: un dossier pour servir la verite, by Francois Foucart, a journalist, offers new evidence suggesting that he was guilty.
Mr Foucart says that there is written evidence that Ms Marchal made grammatical errors with the past tense. He also reveals police evidence that someone had jammed the door to the cellar from the inside with a piece of wood, in between the writing of the first sentence and the uncompleted second.
This could only have been the victim, he says - thus once again pointing the finger of blame at Omar Raddad.