What is the test for determining whether a defendant has committed a constitutional deprivation act?

Deprivation of a constitutional right, within the meaning of section 1983, requires that the defendant perform "an affirmative act, participate[ ] in another's affirmative acts, or omit[ ] to perform an act which he is legally required to do that causes the deprivation of which [the plaintiff complains]." Leer v. Murphy, 844 F.2d 628, 633 (9th Cir.1988) (internal quotation and citation omitted). With respect to causation, the inquiry must focus on the duties and responsibilities of each individual defendant whose acts or omissions are alleged to have caused a constitutional deprivation. Id.