Two men were scheduled for execution in the US tonight, Lawrence Brewer and Troy Davis.In the case of Lawrence Brewer, a white supremacist, there is absolutely no doubt that he was guilty the particularly horrible and brutal murder of James Byrd Jr in 1998 (details are disturbing). The day before the execution, he was quoted in this article openly admitting his guilt and being without remorse. In the case of Troy Davis, there is a great deal of doubt surrounding his conviction for the murder of Mark McPhail in 1989. Convicted on the testimony of nine witnesses, seven of whom have retracted and one of whom is the main other suspect, he has always maintained his innocence, and there is a great deal of information online supporting this claim, including this summary of the case from Amnesty International. Tonight, Brewer was executed, despite the objections of the victim's son, Ross Byrd.We learned only a very short time ago as I write this that Davis has received a last-minute reprieve - though not a stay - meaning that while he will not be executed while the US Supreme Court debates the case, should they decide not to give him a stay, he could be executed at any time in the next seven days. Or hours. It depends how long the Supreme Court take to deliberate and what they decide. If you are against the death penalty, it is quite clear that neither execution can be justified.If you are in favour of the death penalty, this is as clear an opportunity as ever to say: here - you have two men who have been convicted of murder. One is absolutely definitely guilty, as far as we can ever be sure about guilt. There is an enormous degree of doubt over the other conviction. It is highly probable that the man is not guilty. If you are in favour of the death penalty, your question is this: would you kill both men or neither?No system of justice can be perfect. Innocent people will always be convicted from time to time. If you have the death penalty, that means that innocent people will be executed as a result. If you are in favour of the death penalty, you are in favour of innocent people being executed.It is as simple as that.