Diane's point is well-taken: If the evidence is tainted, it's tainted for purposes of conviction, as well as for sentencing, and it's just as tainted if the defendant gets a long prison sentence as it is if he gets a lethal injection. If the conviction is "clean," by contrast, it's clean irrespective of the nature of the sentence he receives.
Yet I think Emily is onto something anyway when she says that she doesn't "want this country to be a place where people are sentenced to die based on a prosecution that is tainted by torture testimony." Death, after all, is different in many ways, some legal, some prudential. I'm willing, for example, to see a conviction sustained on a weaker factual record than the record on which I'm willing to see a capital sentence carried out — notwithstanding the fact that as a purely legal matter, the evidentiary threshold is the same: proof beyond a reasonable doubt.
That's why I've been cheered at times when governors (and President Clinton once) commuted death sentences to life in prison based on residual doubts about the integrity of a trial record but did not act against the conviction itself. Something similar may be at work here. The stakes in the MCA's softening of the traditional rules of evidence are particularly high in light of the availability of capital punishment in this case. Put another way, I think many people would not argue against conviction of someone who had been waterboarded upon capture if the government can prove his culpability without the use of tainted evidence. Many more, I suspect, would argue in principle against his execution , even if the evidence is clean.