It's happened before, it'll happen again. Many people on death row have been proven innocent. These are people who could have been killed by the government if evidence clearing their names hadn't surfaced. They are going to be killed so some power hungry bureaucrat can look good in the eyes of the bloodthirsty American public. Maybe American citizens are more the problem than politicians are.
Politicians are puppets of the public.
They do things that make them popular with the American people. One example I can come up with was when Bill Clinton said that he wouldn't sign any bill into law that would permit same sex marriages. He did this because he knew that gays would not like him for doing that, but almost any republican presidential candidate would do the exact same thing. But, Bill Clinton would win the all important homophobe vote as well. So he offended some gays, but kept their votes, and won some queer bashing morons votes too.