The rules of most regulatory bodies contain provision dealing with how evidence is to be given by witnesses at a hearing, the categories of persons who qualify as vulnerable witnesses, and the use of special measures in the case of a vulnerable witness. Case management powers may provide directions that each party disclose to the other, in advance of the hearing, details of the witnesses on whom they intend to rely and copies of signed witness statements setting out the substance of their evidence. Some bodies provide for the committee or tribunal, on the application of a party or of its own motion, to require a witness to attend a hearing. Rule 34.4 of the Civil Procedure Rules (CPR) provides that the court may issue a witness summons in aid of a tribunal that does not have power to issue a witness summons in relation to proceedings before it.