TERRANCE WILLIAMS, PETITIONER v. PENNSYLVANIA
Supreme Court of the United States, Kennedy, June 9, 2016,
Recusal – Due Process – Under the Due Process Clause there is an impermissible risk of actual bias when a judge earlier had significant, personal involvement as a prosecutor in a critical decision regarding the defendant’s case.

(Dissent – Roberts, joined by Alito – Authorizing seeking death penalty isn’t the same as personal involvement in a case and doesn’t reflect the post-conviction issue raised)
(Dissent – Thomas – Criminal and post-conviction proceedings are separate)

Violation of due process where state appellate judge denied motion for recusal in an appeal from post-conviction despite being the chief prosecutor authorizing the State to seek the death penalty in the underlying case.

Recusal – Recusal is required “when the likelihood of bias on the part of the judge ‘is too high to be constitutionally tolerable.’”
So… that’s helpful…

No Harmless Error – An unconstitutional failure to recuse constitutes structural error even if the judge in question did not cast a deciding vote