I've always been baffled at the Council of Europe fight against the death sentence: on the one hand you have the rights of the prisoner and how a death sentence is too harsh for any crime. On the other hand it's considered to be perfectly okay to send someone to prison for life or for 20+ years, which is often a lifetime sentence anyway. If I were a convicted criminal, I'm pretty sure I'd rather just get the death penalty rather than living in miserable conditions for the rest of my life. Even more so in countries where the penitentiary system is not known for its great facilities.
So what's the rationale for attempting to eradicate the death sentence? Isn't it practically speaking a much more humane punishment than a long prison sentence?
Edit: while the current answers are certainly interesting, I would like to know the official rationale by the Council of Europe, not what the US or other government entities think about it.