The big issue with the death penalty is not an issue of whether it is a deterrent - that question has been answered by a mountain of evidence that indicates the death penatly is not a deterrent at all.
Anyone who has researched this to any degree will tell you that death rows are populated largely by the kinds of people who lack the mental faculties to understand the consequences of an action or to think something through that far.
That question answered definitively, we must now ask ourselves: is it the correct punishment for people who commit the ultimate crime: 1st degree murder.
The answer is a matter of opinion. If you believe that life in prison is the correct punishment, then the discussion stops. This is a discussion of the death penalty, so let's discuss the idea that death IS the correct punishment for those convicted of first degree murder.
If we are going to allow the state to execute people, it is a moral (not to mention legal) imperative to make sure the correct person is apprehended, tried, convicted and executed.
It is a fact of our justice system that the wrong people are often convicted and impriosned. When these misatkes are made known, the convict is freed, and can be compensated. It doesn't give them their time back, but at least it does something.
With the death penalty, you're not coming back. Yet the standard for *conviction* in a death penalty case does not change. A standard which results in many incorrect imprisonments should not be applied to the death penalty.
Some death penalty advocates aruge that a standard of "absolute certainty" be imposed on death penalty cases. This is a tough standard - you'd pretty much have to see a videotape of the murder to be absolutely certain. Even then, it'd be hard to tell on a grainy convenience store video.
The problem with absolute certainty is that of inconsistency. How can you tell someone that they are getting life in prison for being convicted "beyond a reasonable doubt" of second degree murder, but in the next courtroom, a guy is not getting the max sentence for his crime because the standard was different?
Life in prison and death are the same - the person is removed from society forever. The risk of escape is extremely small, yet it must be borne in order to prevent the execution of the wrong person. The only way the death penalty could be logically justified is on a standard of absolute certainty. But this cannot be applied; a justice system can't convict on two different standards - it's inconsistent and illogical. Therefore there are no logical impositions of the death penalty.
The death penalty is worng.