All 3 Uses of

immaterial
in
To Kill a Mockingbird

"Can't see what witness's literacy has to do with the case, irrelevant 'n' immaterial."
p. 200.9 *

immaterial = unimportant

Slowly but surely I began to see the pattern of Atticus's questions: from questions that Mr. Gilmer did not deem sufficiently irrelevant or immaterial to object to, Atticus was quietly building up before the jury a picture of the Ewells' home life.
p. 208.1

"Now let's consider this calmly-" began Atticus, but Mr. Gilmer interrupted with an objection: he was not irrelevant or immaterial, but Atticus was browbeating the witness.
p. 211.8

Definition:

not important, or not relevant

"Immaterial" is a commonly heard objection to introducing evidence or an argument in court.