§ 2034.280.Supplemental expert witness list; expert witness declaration; deposition of expert

The main exchange under Section 2034.260 happens on one fixed date, but expert disclosures do not always land evenly: an adverse party might designate an expert to testify on a subject the responding party had no reason to anticipate and had not retained its own expert to address. This section gives a party a narrow, time-limited chance to respond in kind. Within 20 days after the exchange, a party who took part in it may submit a supplemental list naming experts who will speak to a subject an adverse party's expert covers, but only if the supplementing party had not already retained an expert on that subject before the original exchange.

A supplemental list is not a bare name and address this time. It has to come with an expert witness declaration under subdivision (c) of Section 2034.260, the same qualifications, expected-testimony, and fee disclosures required for the original exchange, along with any discoverable reports and writings the newly added experts have prepared. And because a supplemental expert surfaces later in the case, this section requires the supplementing party to make those experts immediately available for deposition under Article 3, even if the general discovery cutoff in Section 2024.010 has already passed, so the other side is not shut out of testing the new expert's opinion before trial.