SOTO, et al. vs ROSAIA, et al.

CHP's initial designation included police-practices expert Lorenzo Glenn, Officers David 24CV068478: SOTO, et al. vs ROSAIA, et al. 08/13/2026 Hearing on Motion to Augment Record EXPERT DISCLOSURE OR, IN THE ALTERNATIVE, TO RE-OPEN DISCOVERY AS TO EXPERTS ONLY; filed by California Highway Patrol (Defendant) CRS# 403135990769 in Department 517 Cristalinas and David Leonard, and accident-reconstruction expert Dr. Dean Stolworthy, whom CHP designated to testify regarding, among other things, "perception and reaction timing analysis; driver visibility analysis . . . human factors . . . perception-reaction timing; visibility." (Id. ¶ 5 & Ex. C.)

On March 26, 2026, CHP served a supplemental designation adding a second human factors expert, Dr. Erwin Boer. (Id. ¶ 8 & Ex. E.) CHP designated Dr. Boer to testify regarding human factors, including the effect of lighting on the officers’ perceptions and sensations while driving, the identification of hazards, and a pre-impact analysis of driver behavior and vehicle movements. Plaintiffs objected to the designation of Dr. Boer. CHP offered Plaintiffs to designate their own human factors expert; however, they declined the offer.

CHP filed the instant motion on June 30, 2026, seeking leave to designate Dr. Boer as a supplemental expert, to augment its expert disclosure under Code of Civil Procedure section 2034.610, or, in the alternative, to reopen expert discovery. Plaintiffs oppose CHP’s motion. Caltrans has not filed a response.

LEGAL STANDARD

Under C.C.P. § 2034.210, any party may demand a mutual, simultaneous exchange of expert witness information. Once a demand is made, each party serves the other side with a expert witness list and an expert witness declaration for experts who are retained or is an employee of a party and whose testimony is being offered on that basis. (C.C.P. § 2034.260(b)-(c).) The exchange occurs 50 days before the initial trial date, or 20 days after service of the demand, whichever is closer to trial. (C.C.P § 2034.230(b)).

Within 20 days after the exchange, 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.” (C.C.P. § 2034.280(a); see also id. § 2034.280(b)-(c) [additional requirements for supplemental expert disclosures].)

Separate and apart from the above, any party may seek leave to “augment” its expert witness list (1) by adding a newly retained expert and/or (2) to amend its declaration as to a designated expert’s testimony with respect to the general substance of the testimony that an expert previously designated is expected to give. (Code Civ. Proc. § 2034.610.) The motion must be made a sufficient time before the discovery cutoff to allow the new expert’s deposition within that limit; only under exceptional circumstances may it be made later. (Id. § 2034.610(b).)

The court “shall grant leave to augment or amend an expert witness list or declaration only if all of the following conditions are satisfied”:

SUPERIOR COURT OF CALIFORNIA COUNTY OF ALAMEDA

24CV068478: SOTO, et al. vs ROSAIA, et al. 08/13/2026 Hearing on Motion to Augment Record EXPERT DISCLOSURE OR, IN THE ALTERNATIVE, TO RE-OPEN DISCOVERY AS TO EXPERTS ONLY; filed by California Highway Patrol (Defendant) CRS# 403135990769 in Department 517

(a) The court has taken into account the extent to which the opposing party has relied on the list of expert witnesses.

(b) The court has determined that any party opposing the motion will not be prejudiced in maintaining that party's action or defense on the merits.

(c) The court has determined either:

(1) The moving party would not in the exercise of reasonable diligence have determined to call that expert witness or have decided to offer the different or additional testimony; or

(2) The moving party's failure to call the expert or offer the different or additional testimony resulted from mistake, inadvertence, surprise, or excusable neglect, and the moving party sought leave promptly after deciding to call the expert or offer the different testimony, and served the required expert witness information promptly.

(d) Leave is conditioned on making the expert immediately available for deposition, and on any other just terms, including leave to the opposing party to designate additional experts or elicit additional opinions, a continuance, and costs/litigation expenses to the opposing party.

A trial court may not grant leave if any of the above-listed statutory conditions is not satisfied, and late disclosure of experts should be permitted only when absolutely necessary to avoid a miscarriage of justice. (Cottini v. Enloe Medical Center (2014) 226 Cal.App.4th 401, 421-422.) Excusable neglect is a mistake or inadvertence that reasonable care could not have avoided, a surprise that reasonable precaution could not have prevented, or a neglect that reasonable prudence could not have anticipated. (Elms v. Elms (1946) 72 Cal.App.2d 508, 514.)

DISCUSSION

A. Supplemental Designation

Although CHP styles its motion as one to augment, its lead argument asks the Court to approve a supplemental designation under section 2034.280. That designation fails for two independent reasons.

First, section 2034.280 permits a supplemental designation only for an expert who will opine “on a subject to be covered by an expert designated by an adverse party.” (C.C.P. § 2034.280(a).) Here, Plaintiffs designated Erickson; she testified during her deposition regarding the standard of care for CHP officer investigations and the officers’ response to the roadway spill. She did not

SUPERIOR COURT OF CALIFORNIA COUNTY OF ALAMEDA

24CV068478: SOTO, et al. vs ROSAIA, et al. 08/13/2026 Hearing on Motion to Augment Record EXPERT DISCLOSURE OR, IN THE ALTERNATIVE, TO RE-OPEN DISCOVERY AS TO EXPERTS ONLY; filed by California Highway Patrol (Defendant) CRS# 403135990769 in Department 517 offer opinions in the field of human factors. She did not address the effect of lighting on the officers’ perception, and she did not analyze the driving, behavior, or vehicle movements of anyone involved. (Brandi Decl. ISO Opp. ¶ 7 & Ex. D.) The isolated deposition answers CHP quotes were responses to questions posed by CHP’s own counsel, not affirmative human factors opinions.

Because Plaintiffs designated no human factors expert, there is no adverse opinion on that subject for Dr. Boer to rebut. If CHP believed Erickson’s testimony strayed beyond her designation, its remedy was a motion to exclude that testimony, not the designation of an additional expert.

Second, a supplemental designation is available only where the supplementing party “has not previously retained an expert to testify on that subject.” (C.C.P. § 2034.280(a); Du-All Safety, LLC v. Superior Court (2019) 34 Cal.App.5th 485, 497.) In this case, CHP had already retained a human factors expert. Its initial designation of Dr. Stolworthy expressly identified human factors, perception-reaction timing, and visibility among his subjects. (Brandi Decl. ISO Opp. ¶ 5 & Ex. C.) Dr. Boer’s proposed testimony on the officers’ perceptions, the identification of hazards, and driver behavior falls within the same field.

CHP’s attempt to distinguish Dr. Stolworthy’s human factors opinions as limited to perception-reaction and biomechanics does not avoid the bar, because section 2034.280(a) looks to the subject of the testimony, and both experts are designated to opine on the human factors bearing on the officers’ perception and identification of the roadway hazard. The proposed designation is therefore both barred by the statute and cumulative of an expert CHP already disclosed.

The Court concludes that the supplemental designation of Dr. Boer was improper.

B. Augmentation Under Section 2034.620

CHP’s motion fares no better when viewed as a motion to augment under C.C.P. § 2034.620. As noted, there are four mandatory requirements that must be satisfied before a motion to augment can be granted. CHP has failed to carry its burden in that regard.

As an initial matter, CHP has not shown that it would not, in the exercise of reasonable diligence, have determined to call a human factors expert such as Dr. Boer. (C.C.P. § 2034.620(c)(1).) Nor has CHP shown that its failure to designate Dr. Boer earlier resulted from mistake, inadvertence, surprise, or excusable neglect. (Id. § 2034.620(c)(2).) The subjects of Dr. Boer’s proposed testimony, i.e., the perception and identification of roadway hazards, have been central to this case from its inception.

Indeed, CHP’s desire for an expert on human factors is evidenced by its identification of Dr. Stolworthy in its initial disclosure. CHP’s failure to designate Dr. Boer within the time allowed is attributable to its own lack of diligence, not excusable neglect. Because neither condition of section 2034.620(c) is satisfied, the Court may not grant leave to augment. (Cottini v. Enloe Medical Center, supra, 226 Cal.App.4th at pp. 421-422.)

The record also supports the conclusion that CHP failed to act promptly. CHP served the

SUPERIOR COURT OF CALIFORNIA COUNTY OF ALAMEDA

24CV068478: SOTO, et al. vs ROSAIA, et al. 08/13/2026 Hearing on Motion to Augment Record EXPERT DISCLOSURE OR, IN THE ALTERNATIVE, TO RE-OPEN DISCOVERY AS TO EXPERTS ONLY; filed by California Highway Patrol (Defendant) CRS# 403135990769 in Department 517 supplemental disclosure identifying Dr. Boer on March 26, 2026, but did not file this motion until June 30, 2026, roughly three months later. That delay is not the prompt action section 2034.620(c)(2)(A) contemplates and requires.

Because CHP cannot satisfy the diligence and excusable-neglect requirements of section 2034.620(c), the motion to augment must be denied, and the Court need not resolve whether Plaintiffs would be prejudiced under section 2034.620(a) and (b). Leave to augment may not be granted unless every statutory condition is met. (Cottini v. Enloe Medical Center, supra, 226 Cal.App.4th at pp. 421-422.)

To the extent the reliance and prejudice factors are considered, the inquiry looks to whether the opposing party, in reliance on the existing list, is unprepared and cannot be prepared in time. However, a party is not prejudiced merely because a new expert would give testimony adverse to that party. (Dickison v. Howen (1990) 220 Cal.App.3d 1471, 1479.) The Court’s denial of the instant motion does not rest on that factor. Late disclosure of experts should be permitted only when absolutely necessary to avoid a miscarriage of justice, and CHP has made no such showing. (Cottini, supra, 226 Cal.App.4th at p. 422.) The Court finds that augmentation is not appropriate under the facts presented.

C. Reopening Discovery

CHP’s alternative request to reopen expert discovery fails for the same reasons. A party seeking that relief must show diligence, and a strategic or unexplained failure to make a timely designation is not a sufficient reason to reopen discovery. (Cottini v. Enloe Medical Center, supra, 226 Cal.App.4th at p. 421.) For the reasons stated above, CHP has not shown the diligence, or the exceptional circumstances, that would justify reopening expert discovery to accommodate an expert it could and should have designated within the time allowed. That the trial continuance moved the fifty-day expert-disclosure date to September 7, 2026 does not supply the requisite diligence or exceptional circumstances, because the deficiency is CHP’s failure to timely designate, not the trial calendar.

CONCLUSION

Defendant California Highway Patrol's Motion to Augment Expert Disclosure or, in the Alternative, to Re-Open Discovery as to Experts Only is DENIED. CHP’s supplemental designation of Dr. Erwin Boer is stricken, and Dr. Boer may not offer expert opinion testimony in CHP’s case-in-chief. This order does not decide any issue reserved for trial, including any use of expert testimony permitted under Code of Civil Procedure section 2034.310.

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SUPERIOR COURT OF CALIFORNIA COUNTY OF ALAMEDA

24CV068478: SOTO, et al. vs ROSAIA, et al. 08/13/2026 Hearing on Motion to Augment Record EXPERT DISCLOSURE OR, IN THE ALTERNATIVE, TO RE-OPEN DISCOVERY AS TO EXPERTS ONLY; filed by California Highway Patrol (Defendant) CRS# 403135990769 in Department 517 THROUGH ECOURT

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SUPERIOR COURT OF CALIFORNIA COUNTY OF ALAMEDA

24CV068478: SOTO, et al. vs ROSAIA, et al. 08/13/2026 Hearing on Motion to Augment Record EXPERT DISCLOSURE OR, IN THE ALTERNATIVE, TO RE-OPEN DISCOVERY AS TO EXPERTS ONLY; filed by California Highway Patrol (Defendant) CRS# 403135990769 in Department 517 Join by H.323 161.199.138.10 (US West) 161.199.136.10 (US East) Meeting ID: 161 8198 9812