Supplemental expert witness list
20 days after date of the expert exchange, under Cal. Code Civ. Proc. 2034.280(a).
Rule text
Within 20 days after the exchange described in Section 2034.260, any party who engaged in the exchange may submit a supplemental expert witness list containing the name and address of any experts who will express an opinion on a subject to be covered by an expert designated by an adverse party to the exchange, if the party supplementing an expert witness list has not previously retained an expert to testify on that subject.
Calculate this deadline
- Trigger (Date of the expert exchange): Friday, November 6, 2026.
- Exclude the trigger day and count 20 calendar days: Thursday, November 26, 2026.
- That day is a Thanksgiving Day, so the deadline moves to the next court day: Monday, November 30, 2026 (Cal. Code Civ. Proc. 12, 12a, 12b, 10; Cal. Rules of Court, rule 1.10).
Cal. Code Civ. Proc. 2034.280(a)
Within 20 days after the exchange described in Section 2034.260, any party who engaged in the exchange may submit a supplemental expert witness list containing the name and address of any experts who will express an opinion on a subject to be covered by an expert designated by an adverse party to the exchange, if the party supplementing an expert witness list has not previously retained an expert to testify on that subject.Official source
Cal. Code Civ. Proc. 12, 12a, 12b, 10; Cal. Rules of Court, rule 1.10
CCP 12: "The time in which any act provided by law is to be done is computed by excluding the first day, and including the last, unless the last day is a holiday, and then it is also excluded." CCP 12a(a): "If the last day for the performance of any act provided or required by law to be performed within a specified period of time is a holiday, then that period is hereby extended to and including the next day that is not a holiday. For purposes of this section, “holiday” means all day on Saturdays, all holidays specified in Section 135 and, to the extent provided in Section 12b, all days that by terms of Section 12b are required to be considered as holidays." CCP 12b: "If any city, county, state, or public office, other than a branch office, is closed for the whole of any day, insofar as the business of that office is concerned, that day shall be considered as a holiday for the purposes of computing time under Sections 12 and 12a." CCP 10: "Holidays within the meaning of this code are every Sunday and any other days that are specified or provided for as judicial holidays in Section 135."Official source
- Runs from the exchange date, not from service; AMBIGUITY whether 1013 applies when the exchange was made by mail.
- If the clerk's office is closed or inaccessible on the last day (weather, emergency or local closure orders), the deadline may be extended. Check local orders.
This calculator applies the cited rules to the dates you enter. It is not legal advice. Court orders, local rules, and case-specific facts can change a deadline; verify before relying on it. Rule set pending attorney review.
Worked example
Date of the expert exchange on Monday, March 15, 2027, personal service: due Monday, April 5, 2027.
- Trigger (Date of the expert exchange): Monday, March 15, 2027.
- Exclude the trigger day and count 20 calendar days: Sunday, April 4, 2027.
- That day is a Sunday, so the deadline moves to the next court day: Monday, April 5, 2027 (Cal. Code Civ. Proc. 12, 12a, 12b, 10; Cal. Rules of Court, rule 1.10).
Notes
Runs from the exchange date, not from service; AMBIGUITY whether 1013 applies when the exchange was made by mail.
Related deadlines
- Responses to interrogatories (30 days after)
- Responses to requests for production (inspection demands) (30 days after)
- Responses to requests for admission (30 days after)
- Unlawful detainer: responses to interrogatories, inspection demands, requests for admission (5 days after)
- Motion to compel further responses (interrogatories, inspection demands, RFAs) (45 days after)
- Discovery cutoff (complete discovery) (30 days before)
- Discovery motion cutoff (last day for hearing) (15 days before)
- Demand for exchange of expert witness information: last day (70 days before)
Local rules by county
County local rules and courtroom procedures can add to or change this deadline. Pick a county to calculate with them applied.
- Alameda
- Alpine
- Amador
- Butte
- Calaveras
- Colusa
- Contra Costa
- Del Norte
- El Dorado
- Fresno
- Glenn
- Humboldt
- Imperial
- Inyo
- Kern
- Kings
- Lake
- Lassen
- Los Angeles
- Madera
- Marin
- Mariposa
- Mendocino
- Merced
- Modoc
- Mono
- Monterey
- Napa
- Nevada
- Orange
- Placer
- Plumas
- Riverside
- Sacramento
- San Benito
- San Bernardino
- San Diego
- San Francisco
- San Joaquin
- San Luis Obispo
- San Mateo
- Santa Barbara
- Santa Clara
- Santa Cruz
- Shasta
- Sierra
- Siskiyou
- Solano
- Sonoma
- Stanislaus
- Sutter
- Tehama
- Trinity
- Tulare
- Tuolumne
- Ventura
- Yolo
- Yuba
Rules current as of 2026-10-25. Confirm against the official source and any local rule or court order before relying on a date. Rules changelog.