Depositions shall not be ordered for discovery or any other purpose except as specifically provided by statute or rule.
Whenever due to exceptional circumstances of the case it is in the interest of justice that the testimony of a prospective witness of a party be taken and preserved for use at trial, the court may upon motion of such party and notice to the parties order that testimony of such witness be taken by deposition and that any designated book, paper, document, record, recording, or other material not privileged, be produced at the same time and place. If a witness is committed for failure to give bail to appear to testify at a trial or hearing, the court on written motion of the witness and upon notice to the parties may direct that his deposition be taken. After the deposition has been subscribed the court may discharge the witness.