GAC Equipment, LLC, doing business as Austin Crane Service, hired Diamond Hydraulics, Inc. to repair a crane, Diamond rebuilt the crane's cylinder, which later bent while lifting a bridge, and Diamond blamed poor maintenance and improper operation while Austin Crane blamed Diamond.¹ The expert-designation deadline was February 10, 2020, Diamond designated Dr. John Behrendt in time, but Austin Crane did not let Diamond test the cylinder until August 2021, after which Diamond replaced him with Dr. Kevin Macfarlan, 540 days after the deadline, and Austin Crane designated a rebuttal expert 609 days late.² Shortly before the October 2022 trial, which had been reset twice, Dr. Macfarlan quit his job, left Texas for Ohio and refused to testify, and Diamond promptly gave notice and tried to substitute Dr. Michael Hoerner, who worked at the same firm and helped prepare the report, stipulating that he held the same opinions.³

The district court heard the motion 17 days before trial, denied substitution and then continuances, and the case was tried without any causation expert for Diamond, and the jury found for Austin Crane on the contract and warranty claims.¹ The Third Court of Appeals (Austin) affirmed, and the Supreme Court heard argument on December 4, 2025.² On March 27, 2026 it reversed and remanded for a new trial.³

Petition for review from the Third Court of Appeals (Austin); argued December 4, 2025; opinion by Justice Sullivan issued March 27, 2026.⁴

• Diamond:¹ whether it was error to prevent a substituted testifying expert on the key issue of causation when the need to substitute was no fault of Diamond and the expert offered no new opinions, and whether it was error to permit the plaintiff's rebuttal expert when no defense expert was allowed to testify.
• Austin Crane:² whether the trial court abused its discretion under Rule 193.6 in excluding Dr. Hoerner, whom Diamond designated 952 days after the deadline and 31 days before the fourth trial setting, and whether it erred in the timing of its own rebuttal expert's testimony.

A ruling excluding an untimely designated expert is reviewed for abuse of discretion, which occurs when the court acts arbitrarily and unreasonably or misapplies the law to the established facts.¹

Whether the trial court abused its discretion in excluding the substitute expert.

Diamond Hydraulics (Petitioner): The need to substitute arose from no fault of Diamond, the substitute offered no new opinions, and exclusion deprived Diamond of its merits defense on the key issue of causation.¹

Austin Crane (Respondent): The trial court did not abuse its discretion because it considered the mandatory exclusion rule, the arguments of counsel, the fact that the substitution came 17 days before trial and the experts' different fields, and any error was harmless.²

The opinion does not recite the petition's reasons, but the Court granted review to decide whether the district court abused its discretion by finding no good cause for the late designation.¹

• Alvarado standard. Asked yes or no whether it loses under Alvarado's difficult-or-impossible standard, petitioner's counsel answered "Absolutely not." (Oral Argument, 0:34:22)
• Could have deposed. Asked if it could have deposed the newly designated expert, respondent's counsel said yes, sometime in the 34-day period. (Oral Argument, 0:17:13)
• Not enough to refuse. Asked why the expert's refusal to return or accept a subpoena is not enough, respondent's counsel said it does not meet Alvarado's standard of difficult or impossible circumstances. (Oral Argument, 0:14:23)
• Deposition fallback. Petitioner's counsel said treating a deposition as the fallback would force lawyers to take every expert's testimony as a trial deposition, just in case. (Oral Argument, 0:04:27)
• Substitute for live testimony. Asked what offers matter if the expert will not appear, respondent's counsel said the solution is to use his deposition, which counsel called an adequate substitute. (Oral Argument, 0:25:32)
• Broader rule. Asked what broader rule controls, petitioner's counsel said a trial court abuses its discretion under rule 193.6 when it refuses to consider evidence establishing good cause. (Oral Argument, 0:36:58)
• Remote testimony. Asked if Zoom would have been enough, petitioner's counsel said it wanted live expert testimony but would have welcomed Zoom had the expert agreed. (Oral Argument, 0:08:11; 0:09:12)
• Not inadvertent. Respondent's counsel said there were conscious decisions along the way that were not inadvertent. (Oral Argument, 0:30:38)

None noted

Holding

The district court abused its discretion in finding no good cause for Diamond's late designation of a substitute causation expert after its original expert left the State and refused to testify, because good cause is a demanding standard but not an impossible one, and it was met here.¹

Reasoning

Rule 193.6 bars testimony of an expert not timely identified unless the court finds good cause or no unfair surprise or prejudice, and the good-cause standard is demanding but "neither so loose as to 'impair its purpose,' nor so insurmountable as to be a dead letter".² Four reasons made the call easy: Dr. Macfarlan's unavailability was outside Diamond's control and he was beyond subpoena range, Diamond made good-faith efforts and promptly proposed a substitute with limits to minimize prejudice, causation was the cornerstone of the case and turned on technical metallurgy, and the court treated the two late designations disparately by allowing Austin Crane's rebuttal expert over objection and not allowing Diamond's substitute.³ Austin Crane's counterarguments fail, since Rule 193.6(b) allows the court to look to the whole record, Diamond cannot be faulted for failing to anticipate the witness's departure and a deposition is no substitute for live expert testimony, and because good cause is found the Court did not reach unfair surprise or prejudice.⁴

Disposition

Court of appeals' judgment reversed and the case remanded for a new trial.⁵

Vote Breakdown

Majority Opinion by Justice Sullivan

Joined by Blacklock, C.J., and Bland, Busby, Devine, Hawkins, Huddle, Lehrmann, and Young, JJ.

Abuse of discretion, with the party that failed to designate in time bearing the burden to show good cause or lack of unfair surprise or prejudice.¹

Justice Sullivan delivered the opinion of the Court, with no separate writings.¹