Yeah, but I only support the death penalty in extreme cases. Are you going to argue that Osama Bin Laden is inocent?
The only cases I can see death sentence as somewhat justified in would involve :
1-The person represent a non-insignificant risk even behind bars (hostage takings, etc). Possible escape is generally insignificant in 99.99999% of countries.
2-There is overwhelming physical evidence that they are guilty. DNA is prefered in cases where it may apply.
3-The person has claimed responsibility in a formal setting, and does not protest his or her innocence with regard to the act. (Whether or not they claim they cannot be tried for the crime, ala Saddam, is however irrelevant).