Blacks were excluded from the indicting grand jury, which led Hillery to claim that he was denied equal protection rights guaranteed by the Fourteenth Amendment.

Accordingly, when the trial judge is discovered to have had some basis for rendering a biased judgment, his actual motivations are hidden from review, and we must presume that the process was impaired.

Similarly, when a petite jury has been selected upon improper criteria or has been exposed to prejudicial publicity, we have required reversal of the conviction because the effect of the violation cannot be ascertained.

Like these fundamental flaws, which never have been thought harmless, discrimination in the grand jury undermines the structural integrity of the criminal tribunal itself, and is not amenable to harmless-error review.

The history and purposes of the writ, as well as weighty finality interests and considerations of federalism, counsel against permitting a petitioner to renew on habeas a challenge which does not undermine the justness of his trial, conviction, or incarceration.

"[4] After citing cases where the Supreme Court applied harmless-error analysis or an analogous prejudice requirement on this basis, Powell stated: Grand jury discrimination is a serious violation of our constitutional order, but so also are the deprivations of rights guaranteed by the Fourth, Fifth, Sixth, and Fourteenth Amendments to which we have applied harmless-error analysis or an analogous prejudice requirement.