For instance if a person who is unrelated to the parents in a custody case is forced to speak as a witness, because they reside in the same dwelling as one of the parents and the other parent wants to make this person appear to be unsafe around children.
If said parent presented evidence at the trial implicating the witness in a crime(that they haven't been tried for) could the witness then be arrested on the spot or immediately after the trial? Or would that evidence need to be removed from the record and a separate trial need to be begun accusing the witness of the crime?

