CROSSOVER: Texas Supreme Court: Excluding a Substitute Expert for Job-Change Unavailability Can Be Abuse of Discretion Under Rule 193.6 (Good Cause Isn’t ‘Impossible’).

Diamond Hydraulics, Inc. v. GAC Equipment, LLC d/b/a Austin Crane Service, 24-1049, March 27, 2026.

On appeal from Court of Appeals for the Third District of Texas (appeal from the 425th Judicial District Court, Williamson County, Texas)

Synopsis

The Texas Supreme Court held the trial court abused its discretion under Texas Rule of Civil Procedure 193.6 by excluding a substitute testifying expert when the original expert became unavailable shortly before trial due to a job change, relocation out of state, and refusal to testify. “Good cause” is a demanding standard, but it is not synonymous with “impossible”—and it was error to force a party to try the case with no expert testimony at all. The Court reversed and remanded for a new trial.

Relevance to Family Law

Family-law trials routinely hinge on expert testimony—valuation in complex estates, tracing and reimbursement, psychological evaluations, substance-abuse and risk assessments, forensic downloads, vocational employability, and conservatorship-related specialty opinions. This decision is a reminder that Rule 193.6’s late-designation gatekeeping is not meant to become a merits-determinative trap when a party promptly responds to genuine expert unavailability outside its control. For divorce and SAPCR litigators, the opinion is a roadmap for (1) building a “good cause” record to substitute an expert late and (2) defeating an opponent’s exclusion attempt when the real-world event (job change, licensing issue, refusal to cooperate, relocation) arises near trial.

Case Summary

Fact Summary

The underlying dispute was commercial: Austin Crane sued Diamond Hydraulics for breach of contract and breach of warranty after a crane cylinder Diamond rebuilt later bent during use. Causation was the central battleground. Discovery was contentious, including delayed access to inspect/test the cylinder—an issue that compressed expert work into the late stages of the case.

Local rules required expert designations by February 10, 2020. Diamond timely designated an expert, but testing of the cylinder did not occur until August 2021, years into the litigation and only months before trial. Both sides made late expert designations thereafter. Diamond ultimately withdrew its prior expert and designated Dr. Kevin Macfarlan (of KnightHawk Engineering) as its testifying expert; Austin Crane deposed him shortly before trial. Austin Crane then designated its own rebuttal expert late. The case was continued and reset multiple times.

Before the next trial setting, Dr. Macfarlan quit his job, moved out of Texas, and refused to testify—memorializing his refusal and relocation in an affidavit. Diamond promptly notified opposing counsel and sought to substitute Dr. Michael Hoerner, another KnightHawk engineer who had participated in preparing the report, with Diamond stipulating that the substitute would offer the same opinions as Macfarlan. The trial court denied substitution under Rule 193.6, denied continuances, and required Diamond to proceed without any causation expert. The jury found for Austin Crane. The court of appeals affirmed. The Texas Supreme Court granted review.

Issues Decided

• Whether the trial court abused its discretion under Texas Rule of Civil Procedure 193.6 by excluding a substitute expert after the originally designated testifying expert became unavailable shortly before trial.
• Whether the circumstances established “good cause” (and/or negated unfair surprise or prejudice) sufficient to permit late supplementation identifying a substitute expert.
• Whether forcing a party to proceed to trial without expert testimony under these circumstances constituted reversible error warranting a new trial.

Rules Applied

Rule 193.6 supplies the governing framework:

• Tex. R. Civ. P. 193.6(a): Untimely disclosed witnesses/evidence are excluded unless the court finds:
  1. Good cause for the failure; or
  2. The failure will not unfairly surprise or unfairly prejudice the other parties.
• Tex. R. Civ. P. 193.6(b): The offering party bears the burden to prove an exception.

The Court also emphasized controlling standards and precedent:

• Abuse of discretion review: a trial court abuses discretion by acting arbitrarily/unreasonably or misapplying the law to established facts.
• The “good cause” standard is demanding and must not be diluted into routine forgiveness of late designations, consistent with the policy against “trial by ambush.”
• Yet, Rule 193.6 is not meant to make “good cause” illusory; it remains a meaningful safety valve when circumstances truly justify relief.
• The opinion situates Rule 193.6 in the lineage of Alvarado v. Farah Mfg. Co., which stressed strictness to prevent ambush, while recognizing Rule 193.6 later added a second exception (no unfair surprise/prejudice) without eliminating good-cause relief.

Application

The Supreme Court treated the trial court’s ruling as an exclusion decision with case-dispositive effect: Diamond was required to try a causation-heavy case with no expert testimony. Against that backdrop, the Court underscored that Rule 193.6’s strictness cannot become a rigid “no-substitution-ever” doctrine when a properly designated expert becomes unavailable for reasons the party cannot control.

The Court identified multiple reasons the good-cause call “should not have been hard.” First, the unavailability was not manufactured: the expert changed jobs, left Texas, and flatly refused to testify—placing him outside subpoena range and outside practical control. Second, Diamond did not sit on the problem. It acted promptly, notified the other side, sought leave, and attempted to cabin prejudice by stipulating the substitute would hold the same opinions as the original expert and selecting someone from the same firm who helped prepare the report.

The Court contrasted this record with scenarios where “good cause” fails—careless counsel, strategic delay, or passive acceptance of witness problems without meaningful mitigation. Here, the party made good-faith efforts to secure testimony and to minimize prejudice from substitution. In that posture, the trial court’s refusal to allow any expert—combined with denial of a continuance—misapplied Rule 193.6’s “good cause” concept and effectively converted a disclosure rule into a merits-deciding sanction.

Holding

The Court held the trial court abused its discretion by denying Diamond leave to substitute a new testifying expert after Diamond’s previously designated expert became unavailable shortly before trial due to a job change, relocation out of state, and refusal to testify. The Court emphasized that while “good cause” is demanding, it is not an “impossible” standard—especially where the unavailability is beyond the party’s control and the party acts promptly and in good faith.

The Court further held the error was reversible, because the exclusion forced Diamond to proceed without any expert testimony in a case where expert causation evidence was central. The Supreme Court reversed the judgment and remanded for a new trial.

Practical Application

In family cases, late expert fights often arise from real-world disruptions: evaluators retire, therapists refuse forensic testimony, custody evaluators lose neutrality, appraisers become unavailable, or vocational experts take new employment and can’t appear. Diamond Hydraulics is valuable because it frames a substitution request as an equitable, record-driven Rule 193.6 inquiry—not a mechanical deadline enforcement exercise.

Use it offensively and defensively in these scenarios:

• Complex property division (valuation/tracing/reimbursement): If your appraiser or forensic accountant becomes unavailable close to trial, build the record that the unavailability was external, that you moved immediately, and that the substitute is tethered to the same analysis/opinions (or explain precisely why additions are necessary and how you will mitigate prejudice).
• SAPCR custody disputes (best interest experts): Psychologists, supervised visitation providers, and risk assessors sometimes decline to testify once litigation intensifies. This case supports the argument that a party should not be forced to try a best-interest contest without expert evidence when unavailability is unexpected and the party acts diligently.
• Enforcement and modification matters: Vocational and financial experts are frequently needed on ability-to-pay/earning capacity. When a designated expert becomes unavailable due to relocation or employment conflicts, Diamond Hydraulics supports relief where the substitute is promptly disclosed and the other side is given a fair opportunity to depose.
• Trial settings that “float” or repeatedly reset: Family dockets often reset, which can create the exact timing problem here—an expert who was available for the original setting becomes unavailable months later. This opinion is a strong anchor for the proposition that the system’s resets can’t be used to weaponize a disclosure deadline into exclusion when the party’s diligence is evident.

Checklists

Substituting an Expert Late (Build the “Good Cause” Record)

• Promptly notify opposing counsel in writing when you learn of unavailability.
• Obtain a sworn affidavit or declaration from the original expert establishing:
• employment change/relocation details,
• refusal or inability to testify,
• lack of availability for the trial setting,
• (if true) inability to comply even by remote testimony.
• Document your good-faith efforts to secure testimony (emails, call logs, proposed accommodations).
• Move for leave immediately, citing Rule 193.6(a)(1) (good cause) and (when available) 193.6(a)(2) (no unfair surprise/prejudice).
• Offer mitigation: same opinions, same report, same file, same testing, same methodology—identify what will not change.
• Propose a deposition date window for the substitute expert and offer to produce the expert file promptly.
• Request a narrowly tailored continuance if needed (and make a clear record why lesser measures are insufficient).

Defending Against a Late Substitution (Showing Surprise/Prejudice)

• Pin down whether the “substitute” is truly a substitute or a new opinions vehicle.
• Demand a detailed proffer: report, reliance materials, and any new testing/analysis.
• Identify concrete prejudice (not generalized complaints):
• new methodology, new discipline, new opinions, new damages model, new best-interest framework, new valuation date assumptions, etc.
• Seek cure measures short of exclusion (deposition, limited scope order, supplemental report deadline) to strengthen the argument that any remaining prejudice is meaningful and not curable.
• Preserve error by obtaining a ruling and ensuring the court states findings on Rule 193.6 exceptions (or by requesting such findings on the record).

Trial-Court Record Preservation (So the Issue Survives Appeal)

• Make an offer of proof on what the substitute expert will say and why it matters.
• Tie the expert’s testimony to essential elements (causation, valuation, best interest, earning capacity).
• If exclusion is threatened, request:
• a brief continuance,
• reopening limited discovery,
• scope-limiting order, and/or
• remote deposition/trial testimony options.
• Ensure the record shows: timing, diligence, unavailability outside your control, and proposed prejudice cures.

Citation

Diamond Hydraulics, Inc. v. GAC Equipment, LLC d/b/a Austin Crane Service, No. 24-1049, __ S.W.3d __ (Tex. Mar. 27, 2026).

Full Opinion

https://www.txcourts.gov/media/1462490/241049.pdf

Family Law Crossover

This is a commercial case, but the tactical lesson translates cleanly to divorce and SAPCR practice: Rule 193.6 can be used either to (1) prevent “trial by ambush,” or (2) unfairly strip a party of essential expert proof when the problem is genuine unavailability. If your opponent tries to exclude your substitute evaluator/appraiser/forensic accountant because “deadlines are deadlines,” Diamond Hydraulics gives you Supreme Court language to reframe the inquiry: good cause is “demanding,” but it is not a requirement of impossibility, and exclusion that forces trial without any expert can be an abuse of discretion. Conversely, if you are opposing substitution, the case pushes you to develop a real prejudice narrative—new opinions, new methodology, inability to prepare—rather than relying on lateness alone, because the Court signaled it will not tolerate a rigid application of Rule 193.6 that functions as a de facto merits sanction when the moving party acted promptly and in good faith.

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