If our death penalty sytem was a fair one in all fifty states, I'd support it. Right now it is clear we sentence innocent people to death. I'm sure we've actually executed some.
John Allen Muhammad was not one of them. He was rightfully executed.
There are many rational people who kill others. Some of them will not kill others if they are covinced of their immenent demise. Even though these crimes happened in 2002, it is still a good idea to let people know that it will end badly for them.
In addition, it is hard to believe, but murderers grow older and wiser; presumably calmer and become "different people". Then they are let out on the streets again. No sentence can ever be guaranteed to mean what it says except the death penalty.
We need to speed up the trials, make sure the defendants' have the best representation, and make sure there is a fair trial. When actual guilt is not disputed and clear, we should employ the death penalty. Not only for serial, multiple, and "special" crimes. But for "regular" revenge, jealously, anger, and spur of the moment crimes. This can save lives and make America more safer.
I don't say this lightly. I understand the errors that could occur. That's why we should build in safeguards. Also, the idea of killing someone is daunting even if it is the state. But this is truly self-defense on behalf of society.