Probably Shinn v. Ramirez. This is what I sent to some one that was up in arms about it after I looked into it:

Basically in an appeal you can't introduce new evidence unless it meets a particular legal standard (I think it's "clear and convincing"). There's a guy on death row for raping a 4 year old to death who had some bullshit evidence that wasn't introduced by his state provided lawyer. It's basically an expert witness testifying that "he couldn't have done it because it takes 48 hours for someone to die of a ruptured internal organ", but to find it compelling you have to ignore the bruising and other injuries that definitely developed in the time frame that he had the girl in his care and that despite her ultimately fatal internal injuries he never noticed or took her to hospital. Because it is a death penalty case however it got appealed all the way to the federal supreme court, who ruled that the evidence wasn't sufficiently compelling to meet the rules around what evidence can be introduced on appeal. The anti death penalty people have all written their "man on death row prevented from introducing evidence that would have found him innocent" and anyone that just read the headline is up in arms.