(1) The credibility of a witness or of any part of his testimony may be attacked or supported by any party, including the party calling the witness.

(2) Where, before he calls the witness, a party has reasonable grounds to believe that he will want to attack the credibility of the witness or of any part of his testimony, the party shall, out of the presence of the witness, notify the court and every other party of his expectation, except that if the witness is a party the witness need not be notified.