Death Penalty Analysis: Introduction

I recently listened to the Intelligence Squared debate on the death penalty. I didn't have a definite opinion on capital punishment before that, but it helped me organize my thoughts. I'm writing this series to help me organize my thoughts further. As per usual, this is not a formal analysis. All my numbers are rough. I'm just seeing if any of these arguments have any chance at all of being valid.

For the purposes of this discussion, I am considering only people who have been convicted of literally the worst imaginable crime; I'd name one, but someone will come up with a worse one, so just use the worst crime you can imagine. If anyone deserves to be executed, it's these people.

I'm also considering that the alternative sentence for these crimes is life in prison, and I'm assuming that it is better for an innocent person to spend life in prison than to be executed. Admittedly that last bit is arguable, but it's the assumption I'm making.

The critical question, the one that determines this entire debate, is this: what are the odds of an innocent person being convicted?

One study puts that number at 4%. Out of 25 people convicted, one will be innocent. That number is shockingly high. Even if you dispute the actual number (and reasonable people can disagree, especially on capital cases), I don't think anyone would dispute that innocent people are convicted of crimes they didn't commit. If you do so dispute, please consider this list of confirmed wrongful convictions, and this one of wrongful executions. And I'd suggest watching this episode of Brain Games (presently available on Netflix streaming). Any conviction based primarily on eye-witness testimony is inherently suspect.

I've heard four arguments for capital punishment, which I will address independently. All of these are based on a somewhat fictional premise: that sentence is the only variable, and that once sentenced, a prisoner will be executed. In reality, that's not true, but we'll talk about the effects of that difference later. I'm trying to analyze the simple theoretical case before getting to the more complex real one. When we add the complexities back in, we'll see if my arguments change.