The California expert witness exchange: 70 days, 50 days, 20 days — and exclusion if you get it wrong

California procedure · Last verified August 17, 2026

California does not disclose experts automatically. There is no counterpart to Federal Rule 26(a)(2), no report written by the expert, and no default schedule. The whole system runs on a demand — and if no party serves one, no expert information is exchanged at all.

Which means the first question in any California case approaching trial is not "when are experts due." It is "has anyone demanded the exchange, and when."

The demand

CCP 2034.210: after the setting of the initial trial date, any party may demand that all parties simultaneously exchange information about expert trial witnesses. The demand may cover three things:

(a) a mutual and simultaneous exchange by all parties of a list containing the name and address of any natural person, including one who is a party, whose oral or deposition testimony in the form of an expert opinion any party expects to offer in evidence at the trial; (b) if any expert designated by a party under subdivision (a) is a party or an employee of a party, or has been retained by a party for the purpose of forming and expressing an opinion in anticipation of the litigation or in preparation for the trial of the action, the designation of that witness shall include or be accompanied by an expert witness declaration under Section 2034.260; (c) a demand for the mutual and simultaneous production for inspection and copying of all discoverable reports and writings, if any, made by any expert described in subdivision (b) in the course of preparing that expert's opinion.

Subdivision (c) is optional and often omitted. If you want the expert's file, the demand has to say so.

Form — CCP 2034.230(a): the demand must be in writing, must identify the demanding party below the title of the case, and must state that it is being made under this chapter.

Service — CCP 2034.240: on all parties who have appeared.

The two deadlines, and the phrase that decides them

Both key dates are set by the same construction, and it is worth slowing down for.

The demand — CCP 2034.220:

A party shall make this demand no later than the 10th day after the initial trial date has been set, or 70 days before that trial date, whichever is closer to the trial date.

The exchange — CCP 2034.230(b):

The specified date of exchange shall be 50 days before the initial trial date, or 20 days after service of the demand, whichever is closer to the trial date, unless the court, on motion and a showing of good cause, orders an earlier or later date.

"Whichever is closer to the trial date" picks the later of the two candidates, not the earlier. In practice:

Situation	Demand due	Exchange due
Trial set well in advance — the ordinary case	70 days before trial	50 days before trial
Trial set on short notice, so that 70 days before trial is already past or within 10 days of the setting	the 10th day after the trial date was set	20 days after service of the demand

So the numbers most cases run on are 70 and 50. The alternates exist so that a case set for trial in six weeks still has a workable expert schedule.

The demanding party chooses the exchange date and states it in the demand — but the date must be the one the statute produces. A demand naming a date the statute does not permit is a candidate for a motion to quash under CCP 2034.250(b)(1).

What you have to hand over

CCP 2034.260(a): all appearing parties exchange in writing on or before the specified date, either at a meeting of the attorneys or by service under CCP 1011 or 1013.

The exchange must include one of two things — subdivision (b):

a list with the name and address of each person whose expert opinion the party expects to offer at trial; or
a statement that the party does not presently intend to offer expert testimony.

There is no third option. Saying nothing is not a permitted response, and it forfeits your experts.

The declaration — subdivision (c). For any listed expert who is a party, a party's employee, or retained, the exchange must include an expert witness declaration signed only by the attorney for the designating party (or the party, if self-represented), under penalty of perjury, containing:

(1) A brief narrative statement of the qualifications of each expert. (2) A brief narrative statement of the general substance of the testimony that the expert is expected to give. (3) A representation that the expert has agreed to testify at the trial. (4) A representation that the expert will be sufficiently familiar with the pending action to submit to a meaningful oral deposition concerning the specific testimony, including an opinion and its basis, that the expert is expected to give at trial. (5) A statement of the expert's hourly and daily fee for providing deposition testimony and for consulting with the retaining attorney.

Two structural differences from federal practice follow from this. There is no expert report: the narrative is written by counsel, not the expert. And item (4) is a promise you make about someone else's preparation — the expert who shows up unfamiliar with the case puts the declaration's signer in a difficult position.

Reports and writings — CCP 2034.270: where the demand included subdivision (c), all parties produce and exchange, at the place and on the date specified, all discoverable reports and writings made by any retained expert.

Not filed — CCP 2034.290: the demand, the lists and the declarations are not filed. The demanding party retains the originals for six months after final disposition. They are lodged with the court when their contents become relevant to a pending matter.

The supplemental list: 20 days, and one purpose only

CCP 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.

This is a narrow right, and both conditions matter. It exists so that a party surprised by an opposing expert on an unanticipated subject can answer it — not so that a party can add experts on subjects it simply neglected.

If you already designated someone on that subject, you cannot supplement on it. For that you need leave under CCP 2034.610.

The supplemental list comes with its own declaration and all discoverable reports and writings of the new experts. And under subdivision (c), the party "shall also make those experts available immediately for a deposition … which deposition may be taken even though the time limit for discovery … has expired."

That last clause is the reason the supplemental designation is workable at all: it reopens expert discovery for the new witnesses only.

Expert depositions

Who can be deposed — CCP 2034.410: on receipt of an expert witness list, any other party may depose any person on it. The ordinary deposition procedures apply, with the exceptions in this article.

Documents, three business days out — CCP 2034.415: a retained expert whose deposition is noticed under CCP 2025.220 "shall, no later than three business days before his or her deposition, produce any materials or category of materials, including any electronically stored information, called for by the deposition notice."

Three business days — the only place in the deposition scheme that counts that way. Notice the expert's deposition with a document demand and you get the file before you sit down, not at the table.

Where — CCP 2034.420: a retained expert's deposition "shall be taken at a place that is within 75 miles of the courthouse where the action is pending." The designating party may move for a protective order on a showing of exceptional hardship for a more distant place.

That is the reverse of the ordinary rule in CCP 2025.250, which measures from the deponent's residence. For experts, the measurement runs from the courthouse — so designating an expert who lives across the country means producing them near the court.

Expert depositions are exempt from the seven-hour limit under CCP 2025.290(b)(2).

The sanction: exclusion

CCP 2034.300 is the reason all of this is taken seriously:

on objection of any party who has made a complete and timely compliance with Section 2034.260, the trial court shall exclude from evidence the expert opinion of any witness that is offered by any party who has unreasonably failed to do any of the following: (a) list that witness as an expert; (b) submit an expert witness declaration; (c) produce reports and writings of expert witnesses under Section 2034.270; (d) make that expert available for a deposition under Article 3.

Three features of that sentence do the work.

"Shall exclude." Not may. Where the conditions are met, exclusion is not discretionary.

"On objection of any party who has made a complete and timely compliance." Only a party who complied can invoke it. A party who blew its own deadline cannot use the other side's failure.

"Unreasonably failed." This is the qualifier that leaves room for argument, and it is where most disputes actually live. A minor or explicable lapse is not automatically an unreasonable one.

The section is expressly subject to CCP 2034.310 and to the augment/amend and relief articles.

Calling an expert you never designated

CCP 2034.310 permits it in exactly two situations:

(a) That expert has been designated by another party and has thereafter been deposed under Article 3 (commencing with Section 2034.410). (b) That expert is called as a witness to impeach the testimony of an expert witness offered by any other party at the trial.

Subdivision (b) has a limit that decides cases: impeachment "may include testimony to the falsity or nonexistence of any fact used as the foundation for any opinion by any other party's expert witness, but may not include testimony that contradicts the opinion."

So an undesignated expert may say the other side's expert relied on a fact that is untrue. They may not say the other side's expert reached the wrong conclusion. The line is between the foundation and the opinion, and crossing it is what turns permissible impeachment into an excluded opinion.

Adding or changing an expert later

CCP 2034.610(a) lets a party who engaged in a timely exchange move for leave to:

augment its list by adding an expert subsequently retained; or
amend its declaration as to the general substance of a designated expert's expected testimony.

Timing — subdivision (b): the motion must be made "at a sufficient time in advance of the time limit for the completion of discovery … to permit the deposition of any expert to whom the motion relates to be taken within that time limit." Later only under exceptional circumstances. A meet and confer declaration is required.

The standard — CCP 2034.620. The court "shall grant leave … only if all of the following conditions are satisfied":

the court has taken into account the extent to which the opposing party has relied on the existing list;
the court has determined that no opposing party will be prejudiced in maintaining its action or defense on the merits;
and the court has determined either that the moving party could not, in the exercise of reasonable diligence, have determined to call the expert or offer the different testimony, or that the failure resulted from mistake, inadvertence, surprise or excusable neglect and the moving party both sought leave promptly after deciding to call the expert and promptly served the proposed expert information on all appearing parties.

And the price — subdivision (d): leave is conditioned on making the expert available immediately for deposition, and on any other just terms, which the statute lists as including leave for opposing parties to designate additional experts or elicit additional opinions, a continuance of the trial, and an award of costs and litigation expenses to the opposing party.

Sanctions under CCP 2034.630 are mandatory against whoever unsuccessfully makes or opposes the motion, absent substantial justification.

Protective orders against the demand

CCP 2034.250 lets a party served with a demand move promptly for a protective order, with a meet and confer declaration. The listed directions include quashing the demand because it was not timely served, moving the exchange date, dividing parties into sides based on identity of interest so that designations are made by side, and requiring a party or side to reduce its list of retained experts.

The "sides" mechanism is the practical answer to a case with eight defendants who would otherwise designate eight sets of the same experts.

One exclusion from the chapter

CCP 2034.010: the chapter does not apply to exchanges of expert lists and valuation data in eminent domain proceedings, which have their own procedure beginning at CCP 1258.010.

How California compares

	California	Washington	Oregon	Federal
Disclosure trigger	a party's demand	interrogatory — CR 26(b)(5)	none — the ORCP have no expert discovery	automatic — Rule 26(a)(2)
Written report	no — an attorney declaration	no	n/a	yes, signed by the expert
Who signs	the attorney, under penalty of perjury	the party	n/a	the expert
Timing	70 days to demand, 50 to exchange	by case schedule	n/a	90 days before trial
Rebuttal experts	20-day supplemental list	—	n/a	30 days after the disclosure
Expert deposition location	within 75 miles of the courthouse	ordinary rules	n/a	ordinary rules
Documents before the deposition	3 business days	—	n/a	with the report
Failure to disclose	mandatory exclusion — CCP 2034.300	CR 37	n/a	Rule 37(c)(1)

The Oregon column is not an omission. The ORCP contain no expert discovery provision at all — the word "expert" appears in only one Oregon rule, ORCP 47, and there it is the summary-judgment device that lets a party oppose a motion with an attorney's affidavit about an unnamed retained expert. The guide on Oregon discovery covers what that means for building a case.

A short checklist

Diary the demand the day the trial date is set. Seventy days before trial, or the 10th day after the setting if trial is close.
Decide whether to demand reports and writings. CCP 2034.210(c) is optional and does not come along by default.
Calendar the exchange — 50 days before trial, or 20 days after service of the demand if the demand went out late.
If you have no experts, say so in writing. CCP 2034.260(b)(2) makes that a permitted response; silence is not.
Write the declaration carefully. Five required contents, attorney signature, penalty of perjury — and a representation that your expert will be ready for a meaningful deposition.
Calendar 20 days after the exchange for a supplemental designation, and check the two conditions before relying on it.
Notice expert depositions with a document demand — you get the materials three business days ahead.
Comply completely and on time. CCP 2034.300 can only be invoked by a party who did.
If you need to add an expert later, move early. The motion has to leave time for the deposition inside the discovery cutoff, and CCP 2034.620 sets four conditions, all of which must be met.

Where these sections live

This page explains what the Code says. It isn't legal advice, and the discovery cutoff that governs expert depositions is set by CCP 2024.020, which interacts with these dates.

How this guide is sourced. Every procedural statement here is drawn from the text of the rules named above, each of which is reproduced verbatim on its own page on this site. Quoted rule language appears in quotation marks or block quotes; everything else is original writing. Last verified August 17, 2026.

This page explains what the rules say. It is legal information, not legal advice, and it cannot tell you how a rule applies to your situation. Deadlines are often short and some are not extendable — if the outcome matters, talk to a lawyer or your court’s self-help center.