 And even if the false evidence were legally inadmissible yet this need not prevent its being regarded as ‘material’ enough to form the subject of an indictment for perjury.There is, for instance, a rule that when a witness answered answers are to be taken as final, so that no other witness can legally be brought to contradict them.Yet if, by a breach of this rule, some second witness be permitted to give this contradiction, and he gave it falsely, he may be indicted for perjury; for, so soon as the contradiction was admitted, it did affect the credit given to the previous witness, and so became ‘material.’

It seems that the question is not just failure to tell the truth, that determines the materiality of the statement.