37 CFR 11.304: Fairness to opposing party and counsel.

A practitioner shall not:

(a) Unlawfully obstruct another party's access to evidence or unlawfully alter, destroy or conceal a document or other material having potential evidentiary value. A practitioner shall not counsel or assist another person to do any such act;

(b) Falsify evidence, counsel or assist a witness to testify falsely, or offer an inducement to a witness that is prohibited by law;

(c) Knowingly disobey an obligation under the rules of a tribunal except for an open refusal based on an assertion that no valid obligation exists;

(d) Make a frivolous discovery request or fail to make a reasonably diligent effort to comply with a legally proper discovery request by an opposing party;

(e) In a proceeding before a tribunal, allude to any matter that the practitioner does not reasonably believe is relevant or that will not be supported by admissible evidence, assert personal knowledge of facts in issue except when testifying as a witness, or state a personal opinion as to the justness of a cause, the credibility of a witness, the culpability of a civil litigant or the guilt or innocence of an accused; or

(f) Request a person other than a client to refrain from voluntarily giving relevant information to another party unless:

(1) The person is a relative or an employee or other agent of a client; and

(2) The practitioner reasonably believes that the person's interests will not be adversely affected by refraining from giving such information.