At any time after the filing of the charge the court upon motion of any party or upon its own motion may order one or more conferences to consider such matters as will promote a fair and expeditious trial. At the conclusion of a conference the court shall prepare and file a memorandum of the matters agreed upon. No admission made by the defendant or the defendant’s attorney at the conference shall be used against the defendant unless the admissions are reduced to writing and signed by the defendant and the defendant’s attorney. This rule shall not be invoked in the case of a defendant who is not represented by counsel.