I’ll begin by admitting something: I’m opposed to the death penalty. While I’m going to stick to the math here and avoid the normative angle, I’m not going to pretend that my views won’t color my analysis. With that caveat in place, here we go:

I think a lot of people were surprised when they learned that Zacarias Moussaoui, the only person tried thus far in connection with 9/11, was not given the death penalty. I was at first, but then I took a few minutes to think critically about the situation, and now it makes a lot more sense.

Federal death penalty cases are quite complex. There is a trial to determine guilt, a separate trial to determine whether the death penalty could be applied, then a third sentencing trial to determine whether the penalty WILL be applied. It seems at first blush that the admitted mastermind behind the bloodiest attack on American civilians in history would have an open-and-shut case culminating in a date with ol’ sparky. However, his life sentence isn’t terribly surprising when one considers the numbers involved.

A death sentence must be unanimous. Massaoui’s life sentence came as the result of a single holdout. There are a great number of people in the United States who are opposed to the death penalty on moral grounds, but assume for the moment that the vetting process removes these individuals from the pool of potential jurors. Furthermore, assume that the prosecutor is able to pinpoint which jurors are likely to give the death penalty in a given case. It sounds like I’ve just stacked the deck in favor of capital punishment, right? Well, not really.

If I can select one person of a given sentiment correctly 95% of the time, that doesn’t mean that I will get a unanimous decision 95% of the time. In fact, I’ll get a unanimous decision roughly 54% of the time (.95^12=.5404). In other words, the odds of receiving the death penalty in this seemingly open and shut case were roughly five to four. Or, for those challenged at both gambling and math, a little better than 50/50.

It’s very difficult to get twelve people to agree on anything. If you don’t believe me, try ordering pizza the next time you have 11 friends over. Then, imagine how much more complicated it would be if everyone had to eat a slice of the same gigantic pizza. Chances are you’d end up with a cheese pizza or a couple of people opting out and ordering calzones instead.

This isn’t a bad thing. I like calzones. Also, as mentioned above, I prefer life sentences to the death penalty. However, people on both sides of the debate seem to be missing the point. Massaoui pointed to this case as proof that even he could get a fair trial in the US. (I suspect that at this point, Glen Beck’s next book just up and wrote itself.) I would imagine that some on the far left may point to this as a major victory in the fight against the death penalty. Similarly, some on the right may be outraged. None of these responses are really entirely appropriate. Massaoui lives because of a statistical artifact and the extremely conservative nature of requirements of unanimity. He “won” the vote 1-11, not 8-4. Similarly, conservatives need not worry that we’ve forgotten about 9/11 or have lost our will to fight against terrorism. Or, at the very least, these events don’t really buttress such an argument. Again, what we see here is really a statistical artifact. You can’t get 12 people to agree on much of anything.