Should a penalty following a guilty verdict be decided by reason or by emotion? And which is the so-called "American Way" of justice?

You know what I'm talking about--the penalty phase of the trial of the 9/11 conspirator. He's been found guilty and now the jury is hearing evidence to decide on whether he lives or dies.

Despite the strong possibility that a death sentence would turn this guy into a martyr to religious fanatics, I have some problems with the testimony that relies on creating strong emotions in the jury. Reliving the deaths is bound to arouse the jurors past the point of rational deliberation--and is that right? Is that the American Way?

Wouldn't it be better to emphasize the total lack of remorse? the total lack of consideration that none of the people who died on 9/11 had knowingly attacked him in any way, shape, or form?

I personally am categorically opposed to the death penalty, and I hope I would feel the same if the person murdered was someone I cared about deeply.

But this raw appeal to base emotions of retribution bothers me a lot. It's creating a lynch mob mentality.