A lawyer shall not: (a) unlawfully obstruct another party's access to evidence; in anticipation of a dispute unlawfully alter, destroy or conceal a document or other material that a competent lawyer would believe has potential or actual evidentiary value; or counsel or assist another person to do any such act. (b) falsify evidence, counsel or assist a witness to testify falsely, or pay, offer to pay, or acquiesce in the offer or payment of compensation to a witness or other entity contingent upon