(1) A party may serve written interrogatories upon an adverse party either with the petition or at any time after the service of a petition. If a party wishes to serve interrogatories with the petition, the party shall furnish sufficient copies to the court for service with the petition.

(2) The party upon whom the interrogatories have been served shall serve a copy of the answers on the party submitting the interrogatories within the time set forth in ARM 24.5.320, unless the court lengthens or shortens the time. Answers must not be due in less than 30 days from the service of the petition.

(3) If the interrogatories are propounded upon the claimant or any other party who is a natural person, then the party shall sign the answers under oath. If the party is the insurer or other entity which is not a natural person, then the party's attorney or other representative of the party may sign the answers and such answers need not be verified. Whether or not verified, the signature of the person signing the answers constitutes a certification that the answers are complete and truthful to the best of the signor's knowledge.

(4) If the answers to interrogatories are made on behalf of an insurer or some other party which is not a natural person, the party propounding the interrogatories may, after receiving the answers, request that the answers be verified, under oath, by the person employed by the insurer or party, other than an attorney for the insurer or party, having the most knowledge of the subject matters mentioned in the interrogatories. The request must be made in writing but need not be filed with the court. Within the time set forth in ARM 24.5.320, the insurer or other party shall provide the requested verification.

(5) Proof of service of interrogatories and answers thereto must be filed with the court simultaneously with the service of discovery on the other party. Interrogatories and answers thereto must not be filed except by leave of court. When a motion is filed making reference to an interrogatory answer, the party filing the motion shall also submit the interrogatory and interrogatory answer to which reference is made. Answers to interrogatories may be used at trial to the extent allowed by the Montana Rules of Evidence and the Montana Rules of Civil Procedure.

(6) No party shall serve on any other party more than 20 interrogatories in the aggregate, inclusive of subparts. Subparts of any interrogatories must relate directly to the subject matter of the interrogatory. Any party desiring to serve additional interrogatories must file a written motion setting forth the proposed additional interrogatories and the reasons establishing the necessity for their use.

(7) Each interrogatory must be answered separately and fully in writing under oath unless it is objected to, in which event the reasons for objection must be stated in lieu of an answer. Objections may be made because of annoyance, expense, embarrassment, oppression, irrelevance, or other good cause. Objections must be signed by the party making them. The party answering the interrogatories shall set forth a verbatim recopy of each of the interrogatories, followed by the answer or objection thereto.

(8) The court will, except in extraordinary circumstances, sustain objections to numerous and complex interrogatories which are not limited to the important facts of the case and which are concerned with numerous minor details.

(9) An interrogatory is not objectionable merely because it is phrased in the form of a request for admission.