Many lawyers use the terms “supplemental expert” and “rebuttal expert” interchangeably, but, according to the Discovery Act, they are very different. A supplemental expert  is one that was disclosed twenty days after experts have been disclosed and is pursuant to Code of Civil Procedure section 2034.280 and is allowed to provide expert testimony. However, a rebuttal expert’s testimony is limited to rebutting or contradicting an opponent’s  expert’s “foundational facts” that form the basis of their opinion.

California Code of Civil Procedure Section §2034.310 titled “When party may call expert witness who has not been previously designated“states:

A party may call as a witness at trial an expert not previously designated by that party if either of the following conditions is satisfied:

(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. This 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.

The use and limitations of a rebuttal expert are best explained in the cases of Kennemur v. State of California (1982) 133 Cal.App.3d 907 and Fish v. Guevara (1993) 12 CA4th 142. Here are the pertinent points the Courts of Appeals makes in each case:

In Kennemur, the Court of Appel stated “when it comes to impeaching expert witnesses, the distinction between an opinion and a foundational fact–though arbitrary–must be made. . . . In many cases, the ultimate opinion of the expert is based on a series of underlying opinions. Thus, rather than broadly construing what a foundational ‘fact’ is, the term should be strictly construed by the trial court to prevent a party from offering a contrary opinion of his expert under the guise of impeachment.” (Kennemur  at 904)

The rationale for the rebuttal witness statute is that any testimony from any source should be admissible on the veracity of the opposing expert’s opinion.  Therefore, even an undisclosed expert may be permitted to contradict facts upon which opposing experts based their opinion upon.  If opposing party’s experts foundational facts are wrong, then their opinions may not be worthy of belief by the trier of fact. (Cal. Prac Guide: Civil Procedure Before Trial (TRG 2021) 8:1729 citing Kennemur at 924-925)

The court stressed that an undisclosed expert may not go further and offer a conflicting opinion or to “rebut” that given by the opposing experts. (Kennemur at 907)

In Fish, the Court of Appeal stated that “[a] party may call as a witness at trial an expert not previously designated by that party if . . . that expert is called as a witness to impeach the testimony of an expert witness offered by any other party at the trial. This 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.” (now §2034.310(b). Hence, an undisclosed expert may testify to facts which contradict the factual basis for the opinions of other experts but may not give opinion testimony which contradicts the opinions of other experts.” (Fish at 145)

For example, “[a]n undisclosed expert may testify that the foundational facts were different than the opposing expert supposed (e.g., speed of the car, patient’s prior medical history, etc.) and the reasons why they were different.  The term “foundational facts” will be strictly construed to prevent a party from offering a contrary opinion under the guise of impeachment.” (Fish at 146)

According to California Wine Association v. Commercial Union Fire Insurance Co. (1910) 159 C 49 at 56, sur-rebuttal evidence is limited to disproving matters in the opposing party’s rebuttal, rather than reiterating evidence already presented in the party’s case in chief.



If a party failed to serve their expert disclosure statement on time, they may bring a motion pursuant to C.C.P §2034.710 for an order to submit a tardy expert witness list.  This section titled Power of Court to Allow Motion to Submit Tardy Expert Witness states:

(a) On motion of any party who has failed to submit expert witness information on the date specified in a demand for that exchange, the court may grant leave to submit that information on a later date.

(b) A motion under subdivision (a) shall be made a sufficient time in advance of the time limit for the completion of discovery under Chapter 8 (commencing with Section  § 2024.010) to permit the deposition of any expert to whom the motion relates to be taken within that time limit. Under exceptional circumstances, the court may permit the motion to be made at a later time.

(c) The motion shall be accompanied by a meet and confer declaration under Section 2016.040.

For the motion to be granted, the moving party must show:

1.     That the tardy submission was a result of “mistake inadvertence of excusable neglect”.    C.C.P §2034.710(c)(1)

2.     Relief was sought promptly.   C.C.P §2034.710(c)(2)

3.     It served a proposed expert witness disclosure that is in compliance with C.C.P. §2034.260 on all parties.   C.C.P §2034.710(c)(3)

4.     The expert(s) will be made available immediately if leave is granted.   C.C.P §2034.710(c)(3)

5.     The deposition(s) of the expert(s) can be taken before the discovery cutoff   for expert depositions.   C.C.P. §2024.040

6.     There is no prejudice to opposing party’s ability to respond to the new discovery.   Dickison v. Howen, 220 Cal. App. 3d 1471 at 1479-1480.

7.     A declaration that the moving party made a reasonable and good faith attempt to resolve the issue informally prior to filing the motion.   Section 2016.040

In considering the motion, the court must consider all of the above factors.  Denial based solely on the timing of the motion is an abuse of discretion.  See Plunkett v. Spaulding (1997) 52 CA4th 114 at 135-136.

If the court grants the motion, the court may also impose other conditions such  as:

  • Allowing opposing parties to designate additional experts or to elicit additional opinions from previously designated experts.
  • An award of costs and litigation expenses in favor of the opposing party .
  • Order the moving party to pay for any additional cost to obtain an expedited deposition transcript.
  • Ordering a continuance of the trial.

The statutes regarding expert disclosures are based on fair play so facts matter.  In bringing this motion, your need to convince the court that under your circumstances, the motion must be granted. If you are opposing the motion, keep in mind that the denial of the motion sets up an appealable issue. It is in everyone’s best interest that the parties meet and confer and agree on the conditions that the tardy submission can be allowed.

In Shadow Traffic Network v. Superior Court (1994) 24 Cal.App.4th 1067, the Court of Appeal stated that where counsel retains an expert consultant with confidential information concerning the opponent’s case, there is a rebuttable presumption that the expert shared that confidential information with the counsel that retained him or her, which requires disqualification. See Evid Code §606 on the effect of a presumption. To prevent disqualification, the presumption must be rebutted with an affirmative evidentiary showing that no confidential materials were transmitted. This showing has been met by including the writings that were transmitted and what topics were discussed verbally, which would demonstrate that the offending material was not transmitted. However, be mindful that it is not just the precise materials, but also the benefit of the confidential materials that must be rebutted: Continue Reading The Other Side Retained My Consultant – Should They Be Disqualified?

On July 29, 2021, in the case of Braganza v. Albertson’s LLC, (2021) 67 Cal. App. 5th 144, the Fourth District Appellate District affirmed the trial court’s denial of Plaintiff’s motion to continue the hearing for a Motion for Summary Judgment and thereafter granting the defense’s motion. The key: Plaintiff’s counsel sought the continuance on the ground that she needed additional discovery to oppose the motion but did not demonstrate diligence in timely conducting discovery before seeking the continuance. Continue Reading You Must be Diligent in Discovery to get a MSJ/MSA Continued

Sometimes, when you follow the rules regarding the expert witness demand and the initial expert witness disclosure and declaration and are now in receipt of opposing party’s expert disclosure, you find that the opposing party plans to call experts at trial in a subject area which you assumed wouldn’t require expert testimony, or that you hadn’t anticipated. If you didn’t disclose experts on the subject, you can serve a Supplemental Expert Disclosure within 20 days of the exchange of expert witness disclosure. Continue Reading I didn’t know I needed an expert on that…

If a party has timely served a Demand for Simultaneous Exchange of Expert Trial Witness Information pursuant to Code of Civil Procedure section 2034.210, then “all parties who have appeared in the action shall exchange information concerning expert witnesses in writing on or before the date of exchange specified in the demand.”C.C.P. §2034.260(a). Unless there is a court order specifying otherwise, that date for the simultaneous exchange is 50 days before the initial trial date, or 20 days after service of the demand, whichever is closer to the trial date. C.C.P. §2034.230(b).

Continue Reading 50 Days Before Trial—It’s Expert Disclosure Time

The biggest burden in bringing motions to compel further responses is the preparation of the separate statement of items in dispute pursuant to CRC, Rule 3.1345. In my blogs and at seminars, I have advised parties to prepare their meet and confer letters in the format of a separate statement. See my blog “EXHIBIT A—The Meet and Confer Letter.” As a Discovery Referee I have required parties to exchange Discovery in Word format. I find electronic forms for Discovery, especially in Word, are helpful for two reasons: (1) the parties can meet and confer using the “Track Changes” function in Word and hopefully agree on the modifications to the propounded written Discovery, and (2) parties can easily prepare the separate statement of items in dispute if a motion needs to be filed. This electronic Discovery process takes out the grunt work of having to retype the interrogatories, requests for admissions and requests for documents, as well as their responses when preparing or responding to the separate statement when only a hard copy was served.

Continue Reading In Order to Facilitate the Discovery Process–Serve Your Discovery in Electronic Form

Assume you receive the following response to your Requests for Production of Documents:

Responding party hereby incorporates its general objections as if fully stated herein. Responding party objects to this request to the extent it seeks information protected from disclosure by the attorney-client privilege and/or work product doctrine, or any other applicable privilege. Responding party objects as it invades their and third parties’ right of privacy. Responding party objects that the request fails to specifically describe each individual item sought or reasonably particularize each category of item sought. Responding party objects that it is unduly burdensome and overbroad. Responding party objects to this request as it does not seek relevant documents or documents reasonably calculated to the discovery of admissible evidence.  Responding party objects that plaintiff has equal access to these documents. Responding party objects that the request seeks documents already in plaintiff’s possession custody or control. Notwithstanding said objections, no documents.

In reviewing the response, it is likely you are focusing in on the fact that there are garbage objections to your request and that you weren’t provided a privilege log. However, there is another issue that you should take very seriously—the document response is not in compliance with California Code of Civil Procedure section 2031.230.

Continue Reading Nail Down Whether the Documents You are Seeking ever Existed and Where They are Now 

The greatest discovery abuses come from responses to Requests for Production of Documents.  Many responses contain a myriad of garbage objections, fail to contain a privilege log, along with producing documents that are not organized by category. Due to the responding party’s failure to comply with Codes of Civil Procedure § 2031.220, §2031.230, §2031.2400 and §2031.280, a motion to compel further responses and production of documents is the most common motion on the court’s docket. It is also the most time-consuming motion to not only prepare, but for the court to rule on.

On January 1, 2020, Code of Civil Procedure §2023.050 became effective which imposes mandatory sanctions for motions regarding Requests for Production of Documents. This new statute requires the court to impose mandatory sanctions on motions involving requests for production of documents. This sets up a party’s ability to bring issue, evidence and terminating sanctions as there will be an adjudication of prior discovery abuse.

Continue Reading New Discovery Sanction Regarding Requests for Production of Documents

There were three changes to the Discovery Act that became effective on January 1st, 2020 which can be found in Code of Civil Procedure sections  2031.280, 2016.090 and 2023.050. This blog will discuss the change to C.C.P. §2031.280 and its significance.

California Code of Civil Procedure § 2031.280 titled Form in which documents to be produced; Form for producing electronically stored information; Translation of data subdivision (a) states as follows:

Old Statute:

(a) Any documents produced in response to a demand for inspection,  copying, testing, or sampling shall either be produced as they are kept in  the usual course of business, or be organized and labeled to correspond with the categories in the demand.

            New Statute:

 (a) Any documents or category of documents produced in response to a demand for inspection, copying, testing, or sampling shall be identified with the specific request number to which the documents respond.


Responding party can no longer produce documents kept in the “usual course of business.

Continue Reading Make Sure You are Aware of the New Document Response Requirements