Rule 312 - Offers of Proof and Expert Opinionsa. Offers of Proof - Except by agreement of the parties, offers of proof, including expert opinions offered by oral representations of counsel and written statements unsigned by the expert, are presumptively inadmissible as evidence. b. Expert Opinions - Expert opinion evidence shall be permitted by live or video testimony, deposition transcript, written report, affidavit, or disclosure signed by the expert.