The potential execution of an innocent man by Texas (Are you surprised?) in 2004 is getting a lot of play all over the place, sparked by an article by David Grann in The New Yorker. Everyone, from the blogosphere, to web magazines, is getting into the act, and many, if not most are having trouble with the system's seeming lack of concern about the Cameron Todd Willingham case.
The trouble can be summed up very succinctly, I think. People are not sanctioned for being guilty of crimes. They are executed, jailed or fined for being convicted of crimes. Despite (or, as some cynics would tell you, in spite of) the best efforts of the criminal justice system, you may be one without being the other. The Supreme Court has never found "a constitutional right for the actually innocent to be free from execution," because, basically, if shockingly, it limits itself to the issue of conviction.
Amendment VNote that is says: "without due process of law," and not: "unless they are actually guilty of the crime." It's an important distinction, and will remain so until investigative infallibility can be reasonably achieved.
No person shall be held to answer for a capital, or otherwise infamous crime, unless on a presentment or indictment of a Grand Jury, except in cases arising in the land or naval forces, or in the Militia, when in actual service in time of War or public danger; nor shall any person be subject for the same offence to be twice put in jeopardy of life or limb; nor shall be compelled in any criminal case to be a witness against himself, nor be deprived of life, liberty, or property, without due process of law; nor shall private property be taken for public use, without just compensation.