What is the test for an amended complaint in a civil action brought by a plaintiff alleging that he was subjected to deprivation of a federal constitutional right?

If plaintiff chooses to file an amended complaint, he should note that any amended complaint must identify as a defendant only persons who personally participated in a substantial way in depriving him of a federal constitutional right. Johnson v. Duffy, 588 F.2d 740, 743 (9th Cir. 1978) (a person subjects another to the deprivation of a constitutional right if he does an act, participates in another's act or omits to perform an act he is legally required to do that causes the alleged deprivation).