I managed to log in via the laptop!!!!!
Bridget, I agree, I simplified my post partly for ease of reading for anyone who hasn't had the chance to study fibre evidence generally, and partly because I was posting from my phone, which takes me forever at the best of times

The confession, strange as it is, doesn't alter the fact that this conviction was obtained on extremely tenuous evidence - as nugnug points out, even if it could be proven that the fibres from the crime scene and Simon's wardrobe, car etc, were identical (which it can't!) it would still only link the fibres to the car and the wardrobe, and not to Simon himself.
My concern, as always, is that we need criminal cases to be proven beyond reasonable doubt, on solid, verifiable evidence. Invariably, at this stage, I'm asked if I'm suggesting we should let murderers go free, just because we can't prove conclusively that they actually committed the crime. My response to that is, I'm not suggesting it - it's the way our justice system is set up, and for good reason, in my opinion.
However tempting it might be to massage a few facts here and there to nail someone that the police "know" has done/is doing bad things, that opens the door for the same to be done to someone who has done nothing wrong - it's a slippery slope.
At the same time, it allows those who have done bad things to challenge their convictions on the basis that investigations/forensics/legal procedures were flawed, so those people, ultimately, have the chance of walking anyway - I reckon, if we get it right in the first place, we all benefit.
As Bridget pointed out, cases like this come down to expert opinion - the two expert arguments weren't before the jury, so the appeal judges, in effect, second guessed what the jury might have thought, had they heard both arguments. The debate about expert evidence and testimony has been going on for some time, but nothing ever seems to be done about it. We've heard of so many "discredited" experts, and one or two of the cases in which their involvement has resulted in convictions being overturned - usually, there's some statement about looking into the dozens/hundreds of other cases, and that's the last we hear of it.
There were calls a couple of years ago to appoint some sort of gatekeeping role to monitor expert opinion - unfortunately, the suggestion then was that judges become the gatekeepers, which doesn''t seem to be any sort of solution at all!