What @dangillmor said, everyone. And this is not even the first time we know of that Texas has executed an innocent person. As in actually innocent, like, didn't do it -- we're not talking about some technicality of the law here, we're talking about someone who is not guilty of the crime of which they are accused.
My point isn't even that Texas is especially bloodthirsty. It's that if you can find multiple examples from just one state, you can bet that other innocent people have been executed elsewhere in the U.S. too.
And that's not counting all the close calls, where some innocent soul was only finally freed because some student clinic at a law school randomly decided to take up their case (because states never give public defenders enough resources to do even a minimally adequate job).
The death penalty is a mistake. It should be abolished. It's so obvious by now that I hardly know how people manage to argue for its continuance (and yet they do -- in particular, politicians running for office do).
In the meantime, if you'd like to help limit the damage, support an organization like The Center On Wrongful Convictions.