Filed 9/30/24 Richard v. Union Pacific Railroad Company CA2/3

NOT TO BE PUBLISHED IN THE OFFICIAL REPORTS

IN THE COURT OF APPEAL OF THE STATE OF CALIFORNIA

SECOND APPELLATE DISTRICT

DIVISION THREE

TERRENCE RICHARD,

Plaintiff and Appellant,

v.

UNION PACIFIC RAILROAD 

COMPANY,

Defendant and Respondent.

 B322044

 (Los Angeles County

 Super. Ct. No. BC665842)

APPEAL from a judgment of the Superior Court of 

Los Angeles County, Gregory W. Alarcon, Judge. Reversed.

Hildebrand, Mcleod & Nelson, Victor A. Russo, and Charles 

S. Bracewell, for Plaintiff and Appellant.

Pacific Employment Law, Joseph P. Mascovich;

Quinn  Covarrubias, Stephanie L. Quinn, and Mariel 

Covarrubias, for Defendant and Respondent.

_______________________________________

California Rules of Court, rule 8.1115(a), prohibits courts and parties from citing or relying on opinions 

not certified for publication or ordered published, except as specified by rule 8.1115(a). This opinion has 

not been certified for publication or ordered published for purposes of rule 8.1115(a).
2

INTRODUCTION

Terrence Richard fell from a train and broke his leg while 

working as a brakeman for Union Pacific Railroad Company 

(Union Pacific). Richard sued Union Pacific for negligence under 

the Federal Employers’ Liability Act (FELA) (45 U.S.C. § 51 et 

seq.). A jury returned a special verdict for Union Pacific, finding 

the company was not negligent.

On appeal, Richard contends the trial court erred by 

granting Union Pacific’s motion in limine to exclude the 

testimony of Richard’s retained expert, Richard Hess. Hess is a 

retired Union Pacific railroad engineer who had worked for the 

last 15 years of his career on the track where Richard was 

injured. Hess would have testified that when starting a very long 

train on that track, it is necessary to engage the throttle and 

release the brakes simultaneously to avoid excessive “slack 

action” at the rear of the train. “Slack action” is the movement of 

the expandable and retractable coupling spaces between a train’s 

railcars. The length of the train increases the slack, and the 

amount of slack action affects the severity of the shock of train 

movements. Hess further would have testified that immediately 

before Richard’s accident, the locomotive engineer released the 

brakes and then waited 24 seconds before engaging the throttle. 

Hess would have opined that this delay caused a surge at the end 

of the train where Richard was working, making it difficult for 

him to avoid losing his footing.

We conclude that the trial court erred by excluding Hess’s 

testimony. Hess had experience relevant to the subject about 

which he was to testify, and his testimony would have been 

helpful to the jury because it would have assisted the jury in 
3

interpreting the video of Richard’s fall and understanding how 

the locomotive engineer’s actions may have caused a surge at the 

rear of the train. The exclusion was prejudicial because it left 

Richard without a witness to testify to what Union Pacific’s 

locomotive engineer did and why it was dangerous. We therefore 

reverse the judgment for Union Pacific and remand the matter 

for a new trial.

FACTS AND PROCEDURAL BACKGROUND

I. Richard’s injury.

On the evening of February 21, 2016, Richard was working

as a brakeman at Union Pacific’s City of Industry railyard. 

Shortly after 6:00 p.m., Richard, conductor Raymond Salcido, and 

locomotive engineer David Pereyra were assigned to route an 

incoming train from track 801 to the railyard. When the train 

arrived, Richard disconnected the rear locomotive from the back 

of the train. He then climbed aboard the rear railcar and 

directed the locomotive engineer, Pereyra, to pull forward about 

25 car lengths. As the train moved forward, Richard fell from the 

rear railcar, sustaining a compound fracture to his ankle.

Richard’s injury required three surgeries and created ongoing 

physical limitations. 

The train from which Richard fell was more than 7,000 feet 

long and was composed of front and rear locomotive engines and 

105 intermodal railcars—flatbed railcars with double-stacked 

cargo containers on top.

1 The railcars were connected by 

1 For consistency, we will refer throughout this opinion to the 

engines powering the trains as “locomotives,” to the intermodal 
4

“knuckles” that created slack between the railcars, allowing the 

train to go around curves and over hills and valleys. Because of 

its length, the train had a total of about 55 feet of slack between 

the railcars. 

The train was powered by diesel locomotives, which 

generated electricity that was sent through a grid to the axles 

that turned the train’s wheels. The locomotive engineer 

controlled the train’s speed by engaging the throttle. At higher 

throttle settings, the locomotive generated more electricity, 

sending more “tractive effort” to the axles to turn the wheels.2 

The locomotive engineer also controlled the train’s two braking 

systems: (1) the “locomotive brakes” (also called the 

“independent” brakes) that decelerated/stopped the locomotive; 

(2) and the “train brakes” (also called the “automatic brakes”) 

that decelerated/stopped the railcars. The train brakes were

powered by air, which traveled through a brake pipe to each 

railcar. Because of the length of this train, it took about 

20 seconds for the train brakes to fully engage. 

cars as “railcars,” and to the locomotives and railcars together as 

the “train.”

2 “Tractive” means “used for pulling or drawing.” 

(CollinsDictionary.com,

<https://www.collinsdictionary.com/us/dictionary/english/tractive> 

[as of Sept. 9, 2024], archived at https://perma.cc/75GJ-STF9>.)

“Tractive effort” is “the force exerted by a locomotive or other 

powered vehicle on its driving wheels.” (CollinsDictionary.com, 

<(https://www.collinsdictionary.com/us/dictionary/english/tractiveeffort> [as of Sept. 9, 2024], archived at <https://perma.cc/SW59-

PWWM>.) 
5

The track on which Richard fell had an unusual “bowl” or 

“U” shape, such that when a long train was stopped on it, the 

train’s rear cars were on a downhill slope and its front cars were 

on an uphill slope. Because of the track’s grade, the rear railcars 

of a stopped train could “bunch” together, contracting the 

coupling space between the railcars. In that event, the back of 

the train could not begin moving until the slack between the rear 

railcars had been eliminated or “pull[ed]” out. 

Data retrieved after the accident from the train’s event 

recorder or “black box” showed that Pereyra began releasing the 

train brakes at 18:40:59. Twenty-four seconds later, at 18:41:23, 

Pereyra moved the throttle from “idle” to “throttle one.” The 

train brakes were fully released by 18:41:32. Pereyra then 

released the locomotive brake, and at 18:41:51, he moved from 

throttle one to throttle two. The wheels began to move at 

18:42:05, and Pereyra moved the throttle back to throttle one at 

18:42:16. The fastest speed reached by the locomotive before 

Pereyra applied the brakes was 3.6 or 3.7 miles per hour. 

A surveillance video of the train yard on the night of the 

accident (the yard surveillance video) showed Richard falling 

from the rear railcar after the train began moving. 

II. The present action.

A. Complaint.

Richard filed the present action in June 2017, alleging a 

single cause of action for negligence under FELA.

3 Richard 

3 Although injured employees in California generally are 

entitled to workers’ compensation benefits regardless of whether 

the employer was at fault (Lab. Code, § 3200 et seq.), workers’ 
6

claimed the locomotive engineer’s negligent train handling made 

the train suddenly surge forward, causing Richard to lose his grip 

and fall off the railcar’s platform.4 Union Pacific maintained 

there was no surge, and Richard fell because he was improperly 

positioned when he directed the locomotive engineer to begin 

moving the train. Specifically, Union Pacific contended that 

Richard was walking across the railcar’s rear platform when the 

train began moving, which caused him to lose his balance and 

fall. 

B. Union Pacific’s motion in limine to exclude the 

testimony of retained expert Richard Hess.

In January 2022, Richard advised Union Pacific that he 

intended to call Richard Hess as a retained expert at trial to 

testify on “ ‘all aspects of liability,’ ” including “ ‘safe railroad and 

locomotive engineer operating practices’ ” and “ ‘defendant[’s] 

compensation benefits are not available to railroad employees who 

suffer on-the-job injuries. Instead, their right of recovery is 

governed by FELA, which permits recovery only if the employer 

was negligent. (Fair v. BNSF Railway Co. (2015) 238 Cal.App.4th 

269, 275 (Fair); Lund v. San Joaquin Valley Railroad (2003) 

31 Cal.4th 1, 6 (Lund).) An action under FELA may be brought in 

either federal or state court. If a FELA action is brought in state 

court, “state law governs procedural questions, while federal law 

governs substantive issues.” (Fair, at p. 275; Lund, at pp. 6–7.)

4 Richard also claimed that his injuries were exacerbated by 

unsafe conditions on the track where he fell. This claim is not 

relevant to the issues Richard raises on appeal, and thus we do 

not discuss it. 
7

liability in this case.’ ” Hess was a retired Union Pacific 

locomotive engineer who had 42 years of experience operating 

freight trains, including on the track where the accident occurred.

Hess did not prepare an expert report, but he disclosed in writing 

the morning of his deposition that he intended to testify that the 

delay between the time the engineer released the train brakes

and engaged the throttle created excessive “slack action” and 

caused the rear railcar to “suddenly snap forward.” The excessive 

slack action would have been avoided by engaging the throttle at 

the same time the train brakes were released, “allowing no slack 

action [and] creating a smooth start of the rear car.” 

Union Pacific filed a motion in limine to exclude Hess’s 

testimony on the grounds that his proposed testimony did not 

meet the standards for admissibility under Evidence Code5

sections 801 and 802. Union Pacific asserted that Hess had no 

specialized education or training in the field of accident 

reconstruction or injury biomechanics, had never qualified as an 

expert witness, and had no formal training in interpreting 

locomotive event recorder downloads. Union Pacific thus 

contended that Hess was not qualified to interpret the locomotive 

event recorder downloads or to opine that Richard was thrown 

from the train due to slack action or improper train handling. 

Richard opposed the motion in limine. He contended that 

formal education was not a prerequisite for expert qualification; 

“ ‘mere’ experience in a trade, occupation, or craft will qualify an 

expert in his or her field.” Hess had extensive experience as a 

locomotive engineer, which gave him “special knowledge and skill 

5 All subsequent statutory references are to the Evidence 

Code unless otherwise indicated.
8

. . . about operating the same type of freight train at the exact 

same location where this accident occurred.” Moreover, Hess’s 

opinions were based on his review of the yard surveillance video 

taken the night of the accident, which showed the railcar on 

which Richard was standing “jerk forward suddenly before . . . 

Richard fell,” and on Union Pacific’s expert’s testimony about 

what the event recorder data showed. Richard asserted that 

Hess “is well qualified to opine that, assuming [Union Pacific’s 

expert] is correct about what the data shows, it demonstrates 

negligent train handling.” 

The trial court tentatively granted Union Pacific’s in limine

motion, subject to a hearing under section 402. 

C. Section 402 hearing.

The court conducted a section 402 hearing immediately 

prior to opening statements. Hess testified that he worked as a

fireman and locomotive engineer for Southern Pacific and Union 

Pacific Railroad for 42 years. He retired in 2013. Hess had no 

formal training in accident reconstruction, but he trained student 

engineers periodically for about 10 years. 

Hess worked for the last 15 years of his career on the track 

where Richard’s accident took place. When a train is in this 

location, the front part of the train is going uphill and the rear 

part is going downhill. 

Hess reviewed the locomotive’s event recorder data and the 

deposition testimony of Union Pacific’s expert, Mark Pollan. 

Although Hess could not interpret all of the event recorder data, 

he was able to “look at the chart . . . Pollan testified about and 

follow what [Pollan’s] talking about.” Hess noted that Pollan had 

testified that the locomotive engineer, Pereyra, released the train 

brakes at 18:40:59, and then waited 24 seconds before engaging 
9

the locomotive’s throttle. Hess opined that this 24 second delay 

was unsafe because it allowed the brakes on the railcars to 

“almost fully release[]” before the engineer began applying power 

to the locomotive. Hess explained that by “waiting, you are 

letting all of the brakes release on the train totally, which like I 

said, being a part of the train is in a bowl like that, the front of 

the train is going uphill, the middle is around that big Y . . . . 

Nothing is holding it from moving.” In other words, the result of 

releasing the train brakes was that the downward-facing railcars 

at the rear of the train would slide forward into the “bowl” in the 

center of the track. When the engineer then engaged the throttle 

and the train started moving, the rear railcar that had been 

bunched up against the car in front of it surged forward, going 

from “sitting still to four miles an hour.” The surge would “cause 

a jolt” to a person on the rear railcar “and make it hard for him to 

hold on.” 

Hess stated that the proper way to move the train on this 

track was to engage the throttle and release the train brakes

simultaneously. He explained: “[T]he way I made that move, I 

immediately went into power and started releasing so the brakes 

release.” By releasing the brakes and engaging the throttle 

simultaneously, Hess said, the railcars were pulled “gently” and 

“the whole train would move more as one [solid] unit.” 

Hess opined that the jolt caused by the engineer’s delay in 

engaging the throttle was apparent from the yard surveillance 

video. He testified: “[T]he [rear railcar] slowly start[s] to move 

and then it speeds up. And that’s when you see [Richard] fall 

right there because you see that it was going a slower speed and 

then it sped up, and you could see him falling.” If the train had 
10

been operated properly, Hess explained, it “[would]n’t surge like 

that.” 

At the conclusion of the section 402 hearing, the trial court 

excluded Hess’s testimony, finding Hess “has no training or 

experience. He doesn’t have any qualifications that the expert 

witnesses that are going to testify in this case have.” 

III. Trial.

The jury heard evidence over five days in March 2022, as 

follows.

A. Plaintiff’s evidence.

Richard testified that on the evening of the accident, he 

detached the rear locomotive from the train and then climbed 

onto the train’s rear railcar. He adopted a three-point stance by

bracing both feet and holding a grab iron with his left hand while 

holding a lantern in his right hand. He then directed the 

locomotive engineer to move forward. There was a “sudden 

surge” as the railcar on which Richard was standing began 

moving “real fast” and he lost his grip. He attempted to grab 

onto the grab iron near him but was not able to do so. He then 

turned toward the back of the railcar and “almost jumped off . . . 

trying to land” so he would not fall backwards. 

Richard testified he had previously experienced a surge or 

“slack action,” but this one was far “more violent.” He had “never 

experienced any surge like that before in [his] career.” 

Raymond Salcido, the train’s conductor the evening of the 

accident, testified that when a locomotive pulls a train forward, it 

lengthens the train by “drawing slack out between the cars which 

is stretching them, building up the momentum so you can get the 

entire train into motion.” A mild to moderate surge caused by the 
11

“slack action” is expected as a train begins moving. It therefore is 

important to adopt a three-point stance by holding on/bracing 

with two feet and one hand, or with two hands and one foot. It is 

permissible to ride on a railcar platform if a three-point stance 

can be maintained. 

Immediately before the accident, Salcido heard a loud, 

metallic sound from the train Richard was working on.6 He then 

heard Richard say on the radio, “Man down. My leg is broken.” 

He immediately went to where Richard had fallen and saw that 

Richard’s right foot was pinned under the rail. 

Pereyra, the locomotive engineer the evening of the 

accident, testified that Richard radioed him to pull forward about 

25 railcar lengths. Pereyra applied the throttle and released the 

“independent” brake—i.e., the brake controlling the locomotive. 

He moved forward some distance and then heard someone say, 

“I’m hurt.” He turned up the volume on his radio and heard 

Richard screaming that his leg was broken. Pereyra immediately 

applied the brakes and stopped the train. 

Pereyra testified that if a locomotive engineer has not 

properly set the train brakes, “you’ll get [a] boom, boom, boom” 

6 The trial court excluded Salcido’s testimony that if an 

engineer starts a train properly there is not much sound as the 

slack between the railcars is drawn out, but “[i]f it isn’t handled 

properly and the slack action comes out you can hear a lot of 

crashing noises.” The court also excluded Salcido’s testimony that 

if a train is properly handled, the slack action is mild, but with a 

“bad engineer . . . it could get pretty rough.” The court further 

excluded Salcido’s testimony that it would “sometimes but not 

always” be possible to maintain one’s grip if slack action is severe, 

and severe slack action can be “enough to make you lose your grip 

no matter how careful you are being.” 
12

noise and the train can surge. Immediately before the accident, 

Pereyra did not “feel any reverberation or . . . any slack.” He is 

“absolutely certain that [he] did nothing that would have hurt 

anybody.” 

B. Union Pacific’s evidence.

1. James Cramer.

Union Pacific’s transportation manager, James Cramer,

testified that he investigated the accident for Union Pacific. He 

reviewed the data generated by the locomotive’s event recorder,

which showed the speed the locomotive traveled, whether it was 

in forward, reverse, or neutral, and if the brakes were employed. 

Cramer explained that if the locomotive engineer applied 

the brakes and pulled the throttle too hard, “that could create an

issue. [¶] . . . [¶] So . . . what you are looking for is to make sure 

there is no abrupt actions by the locomotive engineer.” Cramer 

concluded that the event recorder data showed “a very textbook 

start. The engineer was very careful, very slow and meticulous 

as he started to make his forward move.” He said: “[W]hat I saw 

on the event recorder . . . was that the engineer released the train 

brakes. As the train brakes released there is air that goes 

through the brake pipe and it [gets] to each car and the brakes

start to release. [The locomotive engineer] went to Throttle 1, the 

first throttle position. There [are] a total of eight. And as he did 

that, there was no movement for several seconds because the 

locomotive has to generate tractive effort on the traction motors 

on each wheel on . . . each ax[le]. So as you see, the tractive effort 

come up, there is still no movement. And then it slowly starts to 

move forward as he goes to Throttle 2. And as he [is] getting

forward movement, very slightly, he goes back to Throttle 1. 
13

Again, I would say he is being very careful. And as movement 

started to move forward – I believe he was maintaining 

Throttle 1, between Throttle 1 and Throttle 2. And the 

movement after that was very steady. Meaning, there was no big 

spikes in speed up or down. It was very steady state across the 

movement I saw.” Cramer concluded: “It was a textbook start. I 

don’t think he could start any slower.” 

Cramer agreed with Richard’s counsel that if the engineer 

mishandles the train, the rear railcar can surge forward with so 

much force that a person can be thrown from the car. He also 

agreed that the event recorder data showed the acceleration of 

the locomotive, not the railcars. 

2. Mark Pollan.

Railroad consultant Mark Pollan testified about the data 

generated by the train’s event recorder immediately prior to the 

accident. In brief, he said that the event recorder showed that 

the locomotive engineer began releasing the train brakes at 

18:40:59, moved the throttle from “idle” to “throttle one” at

18:41:23, had fully released the train brakes by 18:41:32, and 

moved from throttle one to throttle two at 18:41:51. By 18:42:05, 

the wheels had begun to move, and at 18:42:16, the locomotive 

engineer moved the throttle back to throttle one. On the basis of 

this data, Pollan concluded: “There is no train handling issue. 

There is no excessive force. There is no excessive throttle. He 

was actually extremely careful.” 

Pollan also testified that the yard surveillance video was 

not consistent with Richard’s account of where he was standing 

when he fell. Pollan said a frame-by-frame analysis of the video 

showed that when the train began moving, Richard was not on 
14

the side of the car holding on to the handles as he should have 

been, but was instead walking across the railcar’s platform. 

On cross-examination, Pollan disagreed with Richard’s 

counsel that the yard surveillance video showed a “surge”

immediately before Richard fell. Pollan said: “I wouldn’t 

categorize it as a surge. It is an increase in speed and that’s 

what’s going to happen when you begin to move a train. It is 

going to increase in speed.” Pollan also disagreed that the 

amount of slack in this train could have caused the rear railcar to 

surge: 

“[Q]: Could [the] slack result in surge at the end of over a 

hundred cars?

“[A]: So, the posture of the slack at the end of the train 

was that it was bunched and as he starts to pull, it’s going to pull 

that slack out and then once it pulls out then it will take off. If it 

was a different kind of train, . . . [t]hat could cause a whip, a 

massive surge on the ends, but these intermodals are made 

where they don’t have a lot of slack, and you don’t get a big slack 

action. [¶] . . . [¶]

“Q: If the jurors see on the video a surge, if they see with 

their own eyes a surge, are you telling everybody that you 

disagree and there is no surge on this video?

“A: What I see is an increase in speed and it is normal. 

So, I’m not seeing a surge.” 

Pollan also testified that to cause a surge in the movement 

of the rear railcar, there would have to be “a massive surge in 

that tractive effort”—that is, a huge spike in the electricity 

created by engaging the throttle. Pollan “didn’t see that when 

[Pereyra] went from throttle one to throttle two. It [was] a 

normal increase.”
15

Finally, Pollan disagreed with Richard’s counsel that 

Pereyra released the brakes 24 seconds before he engaged the 

throttle. He explained that air travels through the train at 

530 feet per second, so it would take 15 seconds for the air to 

reach the last railcar, and then it would take about another 

5 seconds to pump up the reservoir enough to release the brake 

completely. Accordingly, although Pereyra released the train 

brakes 24 seconds before he engaged the throttle, there was just 

a few second delay from the time the train brakes were fully

released until the throttle was engaged. 

3. Dr. Mark Gomez. 

Dr. Mark Gomez, an injury biomechanic expert, testified 

that given the speed at which the rear railcar was moving, there 

would not have been enough force to pull Richard’s hand off the 

grab iron had he been holding it. 

C. Closing arguments.

In his closing argument, Richard’s counsel argued that the 

accident happened because Pereyra mishandled the train. 

Counsel noted that Pereyra admitted that the proper procedure 

would have been to release the train brakes and apply the 

throttle simultaneously. But Pereyra “didn’t do . . . what he said 

he did”—instead, he released the brakes 24 seconds before he 

applied the throttle. Counsel further argued that the 24-second 

delay “caused the surge you see on the video.” 

Union Pacific’s counsel argued there was no evidence 

Pereyra acted negligently. He urged: “Plaintiff’s evidence with 

regard to Mr. Pereyra’s negligence is—there is nothing. No

expert. We didn’t hear anybody come in and say he was

improperly handling the train. It’s Mr. Richard’s speculation that 
16

something that the engineer did in thousands of feet ahead of 

him [affected] what happened at the rear of the train. That’s 

what you heard from the plaintiff’s case.” (Italics added.) 

Counsel continued: “There are different ways to handle a train, 

whether you release the brakes at this time or another time. The 

point is, these two gentlemen, Mr. Cramer, Mr. Pollan told you

what [Pereyra] did was proper. In fact, it was textbook according 

to Mr. Cramer.” 

D. Verdict.

On March 14, 2022, by a vote of 10-2, the jury returned a 

special verdict finding that Union Pacific was not negligent. The 

trial court entered judgment on May 12, 2022. Richard timely 

appealed. 

DISCUSSION

Richard contends the trial court abused its discretion by

excluding Hess’s expert opinion testimony, and the error was 

prejudicial. We agree.

I. The trial court abused its discretion by excluding 

Hess’s expert testimony.

A. Legal principles.

A person is qualified to testify as an expert “if he has 

special knowledge, skill, experience, training, or education 

sufficient to qualify him as an expert on the subject to which his 

testimony relates.” (§ 720, subd. (a).) An expert may provide 

opinion testimony if such testimony is “(a) Related to a subject 

that is sufficiently beyond common experience that the opinion of 

an expert would assist the trier of fact; and (b) Based on matter 

(including his special knowledge, skill, experience, training, and 
17

education) perceived by or personally known to the witness or 

made known to him at or before the hearing, whether or not 

admissible, that is of a type that reasonably may be relied upon 

by an expert in forming an opinion upon the subject to which his 

testimony relates, unless an expert is precluded by law from 

using such matter as a basis for his opinion.” (§ 801.)

In Sargon Enterprises, Inc. v. University of Southern 

California (2012) 55 Cal.4th 747, 770 (Sargon), the California 

Supreme Court clarified that under section 801, the trial court 

“acts as a gatekeeper to exclude speculative or irrelevant expert 

opinion.” The court explained: “ ‘[T]he expert’s opinion may not 

be based “on assumptions of fact without evidentiary support 

[citation], or on speculative or conjectural factors. . . . [¶] 

Exclusion of expert opinions that rest on guess, surmise or 

conjecture [citation] is an inherent corollary to the foundational 

predicate for admission of the expert testimony: will the 

testimony assist the trier of fact to evaluate the issues it must 

decide?” ’ ” (Sargon, at p. 770.) Accordingly, the trial court must 

“exclude expert opinion testimony that is (1) based on matter of a 

type on which an expert may not reasonably rely, (2) based on 

reasons unsupported by the material on which the expert relies, 

or (3) speculative.” (Id. at pp. 771–772). 

The high court warned, however, that trial courts must “be 

cautious in excluding expert testimony.” (Sargon, supra, 

55 Cal.4th at p. 772.) “The trial court’s gatekeeping role does not 

involve choosing between competing expert opinions. . . . [T]he 

gatekeeper’s focus ‘must be solely on principles and methodology, 

not on the conclusions that they generate.’ ” (Ibid.) In other 

words: “The trial court’s preliminary determination whether the 

expert opinion is founded on sound logic is not a decision on its 
18

persuasiveness. The court must not weigh an opinion’s probative 

value or substitute its own opinion for the expert’s opinion. 

Rather, the court must simply determine whether the matter 

relied on can provide a reasonable basis for the opinion or 

whether that opinion is based on a leap of logic or conjecture. 

The court does not resolve scientific controversies. Rather, it 

conducts a ‘circumscribed inquiry’ to ‘determine whether, as a 

matter of logic, the studies and other information cited by experts 

adequately support the conclusion that the expert’s general 

theory or technique is valid.’ [Citation.] The goal of trial court 

gatekeeping is simply to exclude ‘clearly invalid and unreliable’ 

expert opinion. [Citation.] In short, the gatekeeper’s role ‘is to 

make certain that an expert, whether basing testimony upon 

professional studies or personal experience, employs in the 

courtroom the same level of intellectual rigor that characterizes 

the practice of an expert in the relevant field.’ ” (Ibid.)

We review a trial court’s ruling excluding or admitting 

expert testimony for an abuse of discretion. (Sargon, supra, 

55 Cal.4th at p. 773.) “ ‘The scope of discretion always resides in 

the particular law being applied, i.e., in the “legal principles 

governing the subject of [the] action. . . .” ’ ” (Ibid.) Thus, the 

court’s discretion “is not unlimited, especially when . . . its exercise 

implicates a party’s ability to present its case. Rather, it must be 

exercised within the confines of the applicable legal principles.” 

(Ibid., italics added.)

B. Analysis.

As noted above, the trial court excluded Hess’s expert 

opinion testimony because it concluded Hess “has no training or 

experience. He doesn’t have any qualifications that the expert 
19

witnesses that are going to testify in this case have.” In so 

concluding, the trial court erred.

For purposes of evaluating an expert’s qualifications, 

expertise “ ‘ “is relative to the subject,” and is not subject to rigid 

classification according to formal education or certification.’

[Citation.] Rather, an expert’s qualifications can be established 

in any number of different ways, including ‘a showing that the 

expert has the requisite knowledge of, or was familiar with, or 

was involved in, a sufficient number of transactions involving the 

subject matter of the opinion.’ [Citation.] In sum, with respect to 

expert qualification, ‘[t]he determinative issue in each case must 

be whether the witness has sufficient skill or experience in the 

field so that his testimony would be likely to assist the jury in the 

search for the truth, and no hard and fast rule can be laid down 

which would be applicable in every circumstance.’ ” (ABM 

Industries Overtime Cases (2017) 19 Cal.App.5th 277, 294 (ABM); 

see also Malmquist v. City of Folsom (2024) 101 Cal.App.5th 

1186, 1200.) Once this threshold has been met, “questions 

regarding the degree of an expert’s knowledge go more to the 

weight of the evidence presented than to its admissibility.” 

(ABM, at p. 294.)

In the present case, it was undisputed that Hess had 

42 years of experience as a railroad engineer, including many 

years of experience operating the same kind of train involved in 

this case on the same track where the accident occurred. Hess

testified that he had learned through his experience what the 

safest way was to move a long train in that location—that is, by 

simultaneously releasing the train brakes and applying the 

throttle. Hess also testified that he had learned by experience 

that if he waited to apply the throttle after releasing the brakes, 
20

he would give workers on the back of the train “a rough ride.”

7

And, he said he knew from his experience that if a train was

operated properly, the rear railcar would not accelerate as 

quickly as did the railcar from which Richard fell. In short, 

Hess’s testimony at the section 402 hearing established that Hess 

“ ‘was involved in . . . a sufficient number of transactions 

involving the subject matter of the opinion’ ” (ABM, supra, 

19 Cal.App.5th at p. 294)—that is, Hess’s 42 years of experience 

as a train engineer qualified him to opine on Pereyra’s handling 

of the train. 

Union Pacific urges that the trial court properly excluded 

Hess’s testimony because Hess “admitted he was not relying on 

the event recorder data—the most objective and important 

evidence describing how the train moved just before Plaintiff 

fell.” Not so. Hess specifically testified that he reviewed the 

event recorder data “to see when [Pereyra] was doing throttle 

positions and releasing brakes . . . and the direction he was 

going.” Moreover, Hess’s opinion expressly was based on the 

interpretation of the event recorder data offered by Union 

Pacific’s expert witness, Pollan. That is, Hess’s opinion that 

Pereyra did not safely operate the train was premised on Pollan’s 

undisputed testimony that there was a 24-second delay between 

the time Pereyra released the train brakes and engaged the 

7 Hess testified: “When I was trained we actually had 

cabooses on the rear end with two men in it or maybe more, and 

you had to be careful what you did. If you jostled them too much 

back there you would hear about it. [¶] . . . [¶] That you beat 

them up. It was a rough ride. You know, they wanted a smooth 

ride and you wanted to give them a smooth ride to keep them 

safe.” 
21

throttle. While Union Pacific disagreed with Hess about the 

significance of this data, that disagreement is not a valid basis for 

excluding his opinion testimony. (See Sargon, supra, 55 Cal.4th 

at p. 772 [“The trial court’s gatekeeping role does not involve 

choosing between competing expert opinions”].)

Union Pacific next contends that the trial court properly 

excluded Hess’s testimony because Hess could not interpret the 

event recorder data showing the locomotive’s increase in speed. 

This data is relevant, Union Pacific urges, because “all the 

relevant event recorder data confirms that Mr. Pereyra had very 

carefully started the train’s movement, gradually building up its 

speed without producing a surge.” But the locomotive’s speed 

was irrelevant to Hess’s analysis: As we have said, Hess’s

opinion was that a surge at the end of the train was caused by 

the delay between the release of the train brakes and the 

engagement of the throttle, not the speed at which the locomotive 

accelerated. Because Hess’s opinion did not depend on the 

locomotive’s increase in speed, his inability to interpret that 

portion of the event recorder data did not undermine his opinion.

It was undisputed, moreover, that the event recorder measured 

the acceleration of the locomotive, not the railcars. Union 

Pacific’s accident investigator, Mark Cramer, testified as follows:

“Q: [I]s it correct that you can’t tell from the event 

recorder download exactly how the railcar at the rear of the train 

was accelerating?

“A: That is . . . correct.

“Q: So, if you just look at the download . . . you might not 

see everything you need to see to know what happened here?

“A: You are just getting the information on the movement 

of the locomotive, yes.” (Italics added.)
22

Union Pacific also contends that the trial court properly 

excluded Hess’s testimony because he “admitted he had no 

expertise and training in accident reconstruction” and “had been 

unable to analyze how much force would be required to have 

caused Plaintiff to fall, assuming he had been using a proper 

three-point stance as the railcar began to move.” But Hess was 

not offered to testify about accident reconstruction or to opine 

that the allegedly negligent train handling caused Richard to fall. 

His proffered testimony was much more limited—that Pereyra 

mishandled the train, causing a surge at the back of the train 

immediately before Richard fell. Manifestly, Hess’s lack of 

expertise to testify about some topics does not mean he is not 

competent to testify about other topics.8

Next, Union Pacific contends that the trial court properly 

excluded Hess’s testimony because Richard “hoped to improperly

use Mr. Hess’s statement that similar accidents never occurred 

while he worked as a locomotive engineer.” This assertion is not 

followed by a record citation and has no support in the record. 

Even if the assertion were true, however, it would support a 

limitation on Hess’s testimony, not his wholesale exclusion.

Finally, Union Pacific urges that Hess’s testimony that the 

rear railcar was accelerating too fast was properly excluded 

because it would not have been helpful to the jury. According to 

Union Pacific, “the jury, having viewed the video, would be [able] 

to similarly assess the train’s speed without the aid of expert 

8 Notably, Union Pacific’s train handling expert, Pollan, also 

did not testify about the cause of Richard’s fall. Union Pacific 

called another expert for that purpose, injury biomechanic expert 

Dr. Mark Gomez. 
23

testimony.” We do not agree. Even if the jury could have 

independently evaluated the speed at which the rear railcar 

accelerated, it could not have known whether that degree of 

acceleration was typical when a long train began moving. This 

assessment was particularly significant because Union Pacific’s 

expert, Pollan, testified that any increase shown on the video was

“normal.” 

In sum, it was error for the trial court to exclude Richard’s 

proffered expert evidence that the acceleration Richard 

experienced at the rear of the train was out of the ordinary and 

was caused by mishandling of the locomotive by Union Pacific’s 

engineer, Pereyra. 

II. The erroneous exclusion of Hess’s testimony was 

prejudicial. 

The erroneous exclusion of evidence is grounds for reversal 

only if “in light of the entire record, it is reasonably probable that 

a result more favorable to the appealing party would have been 

reached in the absence of the error.” (Brown v. County of Los 

Angeles (2012) 203 Cal.App.4th 1529, 1550; see also ABM, supra, 

19 Cal.App.5th at p. 293 [“ ‘judgment of the trial court may not be 

reversed on the basis of the erroneous [exclusion] of evidence, 

unless that error was prejudicial’ ”].) Having concluded that the 

trial court erred by excluding Hess’s expert testimony, we must 

consider whether the error was prejudicial. 

The exclusion of Hess’s testimony prejudiced Richard

because it is reasonably probable that a result more favorable to 

him would have been reached in the absence of the error. 

Richard’s theory at trial was that he was injured because Pereyra 

improperly managed the train’s acceleration. But Richard could 

not offer direct testimony about how Pereyra controlled the train 
24

because at the time of the accident he was more than 7,000 feet 

and 105 railcars away from Pereyra. All Richard could testify to 

was his own experience at the rear of the train—that he felt a

“violent” surge that was unlike anything he had ever experienced 

in his career. Hess’s testimony would have allowed him, as the 

party with the burden of proof, to connect the surge he said he 

experienced to the allegedly negligent actions of a Union Pacific 

employee.

The exclusion of Hess’s testimony was especially damaging 

to Richard because two witnesses for Union Pacific, Cramer and 

Pollan, were permitted to testify to their opinions that Pereyra’s 

actions were safe and appropriate. Both experts discussed

Pereyra’s actions in detail and offered the conclusions that “[i]t 

was a textbook start,” “[t]here is no train handling issue,” and 

Pereyra was “extremely careful.” Because the trial court had 

excluded Hess’s testimony, Richard was not able to rebut these 

opinions with a contrary expert opinion. 

Finally, Hess’s exclusion prejudiced Richard’s case because 

Union Pacific highlighted the absence of a plaintiff’s expert in its 

closing argument, telling the jury: “Plaintiff’s evidence with 

regard to Mr. Pereyra’s negligence is – there is nothing. No 

expert. We didn’t hear anybody come in and say he was

improperly handling the train. It’s Mr. Richard’s speculation 

that something that the engineer did in thousands of feet ahead 

of him [affected] what happened at the rear of the train. That’s 

what you heard from the plaintiff’s case.” (Italics added.) In 

short, Union Pacific’s counsel expressly argued to the jury that 

Richard had not met his burden of proof because no expert 

testified on his behalf that Union Pacific’s engineer negligently 

handled the train.
25

For all of these reasons, the trial court’s exclusion of Hess’s 

testimony prejudiced Richard because it left him without an 

expert witness to offer evidence of Pereyra’s alleged negligence. 

Accordingly, the judgment must be reversed.

DISPOSITION

The judgment is reversed and the matter is remanded for a 

new trial. Richard is awarded his appellate costs. 

NOT TO BE PUBLISHED IN THE OFFICIAL REPORTS

BERSHON, J.*

We concur:

EDMON, P. J.

EGERTON, J.

* Judge of the Los Angeles Superior Court, assigned by the 

Chief Justice pursuant to article VI, section 6 of the California 

Constitution.