Do the extra appeals in death-penalty cases cause any innocent people to be exonerated? If so, why not apply them also to people who are sentenced to lengthy or lifetime prison terms? And if not, why bother with them at all?
Wrongful convictions are a problem, to be sure, but someone who dies in prison after rotting there 30 years has his life destroyed just as effectively as someone who is executed a year after conviction. Nothing is done about government officials who knowingly withhold evidence or otherwise act to unjustly convict innocent people. I understand that eliminating the near absolute immunity such people enjoy would open the door to many frivolous lawsuits, but I think it’s pretty clear that grants of absolute immunity often corrupt absolutely.
Despite what death penalty abolition advocates might say, any sentence can be and is appealed. If the death penalty is abolished, these advocates will simply have more time to help felons sentenced to life terms. Since the convicted felon's sentence only gets shorter, it's a no-lose proposition and therefore a no-brainer.