I think the condemned should be able to choose their own demise, just like they do with their last meal. Whatever they want, then the state should accommodate .. ones man's poison and all that.
For me, my own three choices of capital punishment in order of preference, would be an overdose of general anaesthetic, then a Firing squad, then Nitrogen asphyxiation. If the Alabama chap hadnt of held his breath then it would have been over in seconds.
Last meal to be a KFC bargain bucket, 3 Bavarian cream vanilla slices followed by a XL portion of Carte Dor chocolate chip mint ice cream. That is all: