I'm sure this comes to no surprise to any member here, but apparently prosecutors (or police officers) that engage in misconduct in trial are rarely ever punished, and are sometimes rewarded instead, even if the misconduct sends innocent people to jail. In this case, it seems as though just a sliver of justice was finally obtained, so many years later.
http://www.huffingtonpost.com/mark-godsey/for-the-first-time-ever-a_b_4221000.html
Antonin Scalia is on record as saying that there is no proof America ever executed an innocent man. Weasel words if I ever heard any.
The Innocence Network has won the
exoneration of some 250 people in recent years, mainly by forcing DNA testing. Some of those people were on death row. The man in the OP was on death row.
Some prosecutors fight tooth-and-nail to prevent the Innocence Network from re-opening a case. A common refrain from prosecutors fighting the Innocence Network is, "He was convicted by a jury of his peers..."
Back in the 1990's, Todd Wallingham was convicted of capital murder based in large part on the testimony of arson experts (his kids died in a house fire). He was eventually put to death. While he was on death row, the "science" of burn patterns that was used to convict was called into question by the arson investigation industry. Basically, they figured out certain burn patterns on floors were not caused by accelerants (gasoline, kerosene); they were cause by super-heated air charging across a ceiling with sufficient velocity to travel down the walls and burn the floor. This was all developed while Wallingham was still on death row. Texas refused to review the case in light of the new discoveries, and executed him. Notably, the warden in charge of killing Wallingham has gone public saying he is no longer convinced Wallingham was guilty. Now
that is saying something. Radley Balko covered this case quite a bit.