Here is the opinion in Mitchell v. United States.

Judge Christen noted that this is the first intra-tribal carjacking crime to result in death:

I join the majority’s considered opinion in full, but write separately because the lengthy history of this case may make it easy to lose track of the fact that Mitchell did not receive the death penalty for his murder convictions. Mitchell was sentenced to death because, in the course of committing their atrocious crimes, he and his accomplice also committed a carjacking. In my view, it is worth pausing to consider why Mitchell faces the prospect of being the first person to be executed by the federal government for an intra-Indian crime, committed in Indian country, by virtue of a conviction for carjacking resulting in death.

Concurring Judge Hurwitz called on the AG to reconsider this matter:

I write separately to stress a point aptly made earlier in the long history of this case by Judge Reinhardt. See Mitchell v. United States, 790 F.3d 881, 894–97 (9th Cir. 2015) (Reinhardt, J., dissenting in part). The heinous crimes that gave rise to this case occurred entirely within the territory of the sovereign Navajo Nation. The defendant is a Navajo, as were the victims. The Navajo Nation has, from the outset of this case, opposed imposition of the death penalty on the defendant, as have members of the victims’ family