Most California employment lawsuits that head toward trial turn into a battle of experts on lost wages, emotional distress, or wage and hour damages. Under Code of Civil Procedure section 2034.300, the trial court “shall exclude from evidence the expert opinion of any witness” offered by a party that unreasonably failed to list the expert or follow the exchange rules. Once either side demands an exchange, the dates are fixed by statute. Missing them can leave an employer without a damages witness.
When can a party demand an expert exchange?
After the trial date is set. Section 2034.220 says a party must make the 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.” No leave of court is needed.
The exchange date follows. Section 2034.230(b) sets it at “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 orders otherwise for good cause. Continuances don’t automatically reset it, since the statute keys to the initial trial date, and parties often stipulate or move to change it.
What must the exchange include?
A list, and often a declaration. Under section 2034.260(b), each party serves either a list of experts it expects to call or “A statement that the party does not presently intend to offer the testimony of an expert witness.”
For retained experts, and for experts who are parties or employees, subdivision (c) requires a declaration under penalty of perjury. It covers qualifications, “the general substance of the testimony,” a representation that the expert “has agreed to testify at the trial,” a representation that the expert will be ready for “a meaningful oral deposition,” and the expert’s hourly and daily fees.
That second item catches employers. An HR director or payroll manager who’ll give opinion testimony about pay practices may need to be designated with a declaration, because section 2034.210(b) covers an expert who “is a party or an employee of a party.”
What kinds of experts come up in employment cases?
Damages experts, mostly. In wrongful termination and discrimination cases, the plaintiff usually designates an economist for lost earnings and benefits and often a mental health professional for emotional distress. The defense needs answers to both, or a strategy for cross-examining without them.
Wage and hour class and PAGA cases rely on statisticians and data analysts who build damages models from time and payroll records. A defense expert who can show sampling errors or wrong assumptions often moves settlement value more than any legal argument. Industry practice experts, such as HR consultants, appear less often and face more admissibility challenges.
Can a party add experts after the exchange?
In limited cases. Section 2034.280(a) lets a party serve a supplemental list within 20 days naming experts “who will express an opinion on a subject to be covered by an expert designated by an adverse party,” but only “if the party supplementing an expert witness list has not previously retained an expert to testify on that subject.”
That rule rewards planning. A defendant that designates no economist expecting the plaintiff to do the same can add one if the plaintiff does. A defendant that designates a vocational expert can’t use the supplemental list to add a second one on the same subject.
Expert exchange deadlines at a glance
| Step | Deadline | Source |
|---|---|---|
| Demand for exchange | 10 days after trial date set, or 70 days before trial, whichever is closer to trial | CCP 2034.220 |
| Exchange date | 50 days before initial trial date, or 20 days after demand, whichever is closer to trial | CCP 2034.230(b) |
| Supplemental list | Within 20 days after the exchange | CCP 2034.280(a) |
| Exclusion on objection | Unreasonable failure to list, declare, produce, or make available | CCP 2034.300 |
The firm’s page on trial defense for California employers describes its work defending employment cases through trial.
Before the expert exchange in an employment case
- Preserve the payroll, timekeeping, benefits, and personnel data any damages expert will need, in native format.
- Calendar the demand and exchange dates as soon as the trial date is set, and confirm the EPLI carrier’s approval process for expert retention.
- Identify the employees who may give opinion testimony, and decide early whether any of them must be designated.
- Pull the plaintiff’s post-termination job search and earnings records, and the medical records produced so far.
- Talk to counsel about retaining consulting experts well before the exchange date, so their work shapes discovery.
Expert witness questions from employers
Should we retain an expert even if the plaintiff hasn’t?
Often, as a consultant. A consulting expert’s work generally stays protected unless that expert is designated. Early analysis of lost wages or class damages shapes discovery and settlement, and the decision to designate can wait until the exchange.
What happens if the plaintiff misses the exchange?
The employer can object at trial and ask the court to exclude the expert under section 2034.300, but only if it made “a complete and timely compliance” itself. Courts may allow late designations on motion, so the objection should be raised promptly.
Can our HR manager testify without being designated?
As a percipient witness about what happened, generally yes. Opinion testimony about industry standards or calculations is different. If the testimony is opinion, check whether designation and a declaration are required.
Do we have to pay to depose the plaintiff’s expert?
Generally yes. Under section 2034.430(b), a party deposing a retained expert “shall pay the expert’s reasonable and customary” fee for the time spent. The fee schedule in the declaration helps budget that cost, which can be significant in class cases.
If your company is approaching trial in an employment case
If your company is defending a wrongful termination, discrimination, or wage and hour case with a trial date set, the expert exchange is often the point where the case’s real value becomes clear. Rosenberger + Kawabata represents employers defending employment lawsuits and claims through its business litigation practice, including claims involving disputed lost wages and emotional distress damages. Contact Rosenberger + Kawabata online for a confidential consultation, or call (310) 894-6921.
Sources
The statutes are Code of Civil Procedure sections 2034.210, 2034.220, 2034.230, 2034.260, 2034.280, 2034.300, and 2034.430.
This post is general information about California and federal employment law as of November 7, 2026. It is not legal advice, and reading it does not create an attorney-client relationship. Employment statutes, regulations, and court decisions change often, and the outcome of any claim depends on its facts. Past results do not guarantee future outcomes.