Personally i think he should just get life in prison with no chance of parole and not the death penalty.
I'm opposed to capital punishment as a whole, it's just so wrong, nobody (Barring the Boondock Saints) has the right to take the life of someone else, which applies both in the case of taking a life through murder, or taking a life through a decision to issue the death penalty.
If someone's done something that ultimately :Ded up, also, what's the point in just killing them. Sure, they're not leeching taxpayer money for the rest of their lives, but at least you have the comfort in knowing that for the rest of their life they will be in a living hell, and for murder, they deserve that far more than the "easy way out" of capital punishment. It's one of the cases where i would say that "death is too good for them".
But as for the lack of solid evidence, yeah, that's a tad worrying. You can have character witnesses or assumptions up to the arse, but without solid proof, you can't just sentence someone like that, but at least from what i read, the process of working through the backlog of death row where he is will take some decades, and if any evidence proving his innocence does crop up, he's got a long as hell time to prove it, it's not like they're taking him outside the courtroom and killing him there.