Final answer:
Courtroom etiquette does not include declining to respond to the defense attorney, as every witness is expected to answer questions from both the prosecution and defense in a fair trial.
Step-by-step explanation:
The courtroom etiquette rule that is not required is to decline to respond to the defense attorney. The Sixth Amendment grants the accused the right to confront and cross-examine witnesses presented by the prosecution, hence it is expected and proper for a witness to answer questions posed by the defense. It is part of the fair trial process to allow both sides, the prosecution and the defense, the opportunity to question witnesses.