At no point has Sion Jenkins stated the police 'framed him'. Good old BW has a book out there that 'speculates' far more than did those closely involved in the case, but a boring science argument doesn't get a publishing deal. And this appeal DID make new case law...
The 'mystery man' was a semi-vagrant who spent a great deal of time by the children's play area in Alexandra Park (opposite the house) and near the badger sett at the far end of the gardens. One of his main obsessions was carrier bags. A tiny piece of a carrier bag had been forced up to the bridge of Billie-Jo's nose (I believe with the tent peg). This evidence was in the pathologist's report and available at the trial, but no-one had considered the full ramifications. It did not become 'all important' to the trial or subsequent appeals. However, it was of the utmost importance to friends and neighbours of Sion as it gave them considerable cause for grave doubt and the impetus to rally on his behalf.
Investigations have been made and there are strong indications that the 'mystery man' is deceased.
The evidence that released Sion actually related to 'blood spatter' - basically whether Billie-Jo was alive when microscopic blood particles were airborne onto his clothing, or whether they could have been produced when attempts were made to revive an already dead child.
Sion was not found 'not guilty' on appeal. Appeal led to two re-trials, with hung juries in both instances, largely due to the technical nature of the arguments presented. After the second re-trial the prosecution decided it could no longer pursue the case and Sion was effectively released on a technicality, hence his failure to receive any compensation for wrongful imprisonment.
As someone who (some 2 years after conviction) supported Sion, yet works within the legal profession, I have to be honest and admit that I cannot categorically state his innocence or guilt. However, given the forensic arguments - and, for me, the carrier bag - I believe justice has been served in Sion's case.
Whether justice has been served for Billie-Jo is a different issue.