(1) Every person called as a witness in a hearing shall swear or affirm that the testimony he or she is about to give in the hearing shall be the truth according to the provisions of RCW 5.28.020 through 5.28.060.

(2) The hearing examiner or court reporter may administer the oath or affirmation to the witness.

(3) Testimony by affidavit is not admitted at a trial board except for good cause shown, or as otherwise permitted in these rules, as provided in a prehearing conference statement or by stipulation of the parties.

(4) The refusal of a witness to answer any question which has been ruled to be proper shall, in the discretion of the hearing officer or board, be grounds for striking all testimony previously given by such witness on a related matter.