When Judge Bybee (joined by Judge Rawlinson) writes the majority opinion in a death penalty habeas case, and grants relief, you should already have a very good sense that he's right. Even if Judge O'Scannlain dissents.
That's the case here.
It's a pre-AEDPA case. Judge Bybee expressly notes in a footnote that the result would go the other way under AEDPA. But since there's a circuit case on point, Burton gets a new trial.
Mind you, Burton's been on death row for thirty-two years. That's a long time for a case to work its way through the state and federal systems. Especially for, as here, a first habeas petition.
But it is what it is.