The Supreme Court rejected the final appeal for clemency on behalf of Troy Davis. This despite the surprisingly weak eye witness testimony (much of which has since been retracted) which initially convicted him. This past year the United States criminal justice system executed 46 people, almost twice the number that was executed in Saudi Arabia. (Who woulda thought?) But still, that is beside the point for the present case. We can debate the morality of killing those who are guilty beyond a reasonable doubt. But surely we can all agree on the immorality of killing those where there is reasonable doubt of guilt.
Interestingly, even if Troy Davis is guilty, the act of executing him given the evidence of his guilt (or lack thereof) is unconscionable.
Consider an illustration. You're driving home when you see what looks like a dummy lying on the road. You drive over it instead of swinging onto the shoulder or stopping to take a closer look. In fact, it could have been a human person. There was reasonable doubt that it was in fact a dummy. What if it was a person?
Let's say that you decide to drive back later and check. Whew! Tt was a dummy after all! That discovery may get you off legally, but it doesn't get you off morally. You are still guilty for driving over something that, given the available evidence of the time, very well could have been a human being. And that is an unconscionable act.
Given that the evidence for Troy Davis' guilt is nowhere near beyond a reasonable doubt, the act of executing him is objectively an unconscionable act, even if he is guilty.