If you're a Cannan-sceptic, I think in general you start from much further back in terms of what you assume to be known or true. Considered critically, the entire HR sighting looks so questionable as to be worthless for a number of reasons.
First, he said he saw a woman and a man, but he never said he thought he saw SJL. That assumption originated with the police and was stated as a fact at the Tuesday press conference, but it was not based on what HR said he saw.
Second, he said he saw them coming out of a house, but there is no eg. fingerprint evidence I've ever heard that SJL ever went in that house. DV indicates (p99 of his book) that it was forensicated on 29 July. If so, when have the police ever said they have forensic evidence she was inside? I believe the answer is 'never'. It follows that if SJL never went inside, HR did not see SJL.
Third, the man he describes cannot have been the man who drove SJL's car because HR thought he was about 5'8". Someone of that height wouldn't have needed to move a seat positioned to suit a 5'6" woman. It was not moved to that position by a Sturgis colleague either, because per AS' book, the last driver before SJL was James Calvert, who he says is "a small man".
Fourth, elements of HR's account were exaggerated either by HR himself or by MG on his behalf, and then retracted. In either case, it was clearly suggested to him right away that he had witnessed part of an abduction, either by MG saying his colleague was missing or by the police later wanting more details. So he's been coached.
Fifth, the routinely-cited, supposedly corroborating sightings are IMO cherrypicked, actually do not corroborate HR, and exclude those that contradict him. One by ND1 was reported fairly soon, but described a 6' man with a broken nose, and he wasn't sure when he saw the couple between 12 and 4. Another, a Spanish schoolteacher, reported a man in his 40s with a suntan. All these accounts are mutually contradictory. Another, from ND2, came in 2 weeks after the initial publicity and simply repeated the whole police account word for word without adding anything new at all. The only two sightings TV documentaries ever mention are ND1 and ND2; the others, who undermine them, are simply ignored.
Sixth, the HR sighting does not identify anyone in enough detail to be useful. It's not enough to point at the pencil sketch and say, That proves Mr Kipper was Cannan. The sketch could be argued to be practically anybody: Uri Geller, Shakin' Stevens, Nicolas Cage, or of course MG, which is IMO who it actually was.
