Does Heck's 'necessarily imply' standard bar a § 1983 suit only if success would 'necessarily require' plaintiff to negate the underlying conviction, or is it enough that prevailing on the § 1983 claim would 'impugn,' 'tend to undermine,' or 'cast a shadow over' the conviction?

QUESTION PRESENTED In Heck v. Humphrey, 512 U.S. 477, 486-87, 486 n.6 (1994), the Court held that a claim under 42 U.S.C. § 1983 is barred—even if it does not seek damages directly attributable to conviction or confinement—if success in the action would “necessarily imply” the invalidity of a plaintiff’s conviction or sentence, unless the conviction has already been reversed, expunged, or otherwise set aside. The Ninth Circuit, sitting en banc, narrowly interpreted Heck to bar a § 1983 action only if success would “necessarily require” plaintiff to prove the unlawfulness of the underlying conviction. The question presented by this petition is: Does Heck’s “necessarily imply” standard bar a § 1983 suit only if, as some circuit courts have held, success would “necessarily require” plaintiff to negate the underlying conviction, or is it enough, as other circuits and California appellate courts have decided, that prevailing on the § 1983 claim would “impugn,” “tend to undermine,” or “cast a shadow over” the conviction?