It seems that Mr McKay is playing the unsafe conviction card as he is unable to prove it is a wrongful conviction. This is the old favourite among lawyers and barristers when all they have to do is put a certain amount of doubt in the minds of the appeal court judges. I personally find this quite reprehensible.
To be fair to Mr McKay there is only so much he can do on a pro bono basis. This case will be costing him more and more time and money the longer he represents Jeremy Bamber, money he can ill-afford to lose.
I do agree however that the only possible light at the end of the tunnel for Mr Bamber is for the Court of Appeal to rule that the conviction is somehow unsafe. Personally, I don't see this happening irrespective of PII or the other more recent arguments being put forward by his legal team.
It should also be remembered that an unsafe conviction is not a declaration of innocence. Consequently the appellant would be most unlikely to ever receive compensation.