Texas High Court Limits Interdependent Expert Opinions

June 09, 2015

Experts may not rely on the unreliable opinions of other experts.

In a recent opinion in Gharda USA, Inc. v. Control Solutions, Inc., No. 12-0987, --S.W.3d--, 2015 WL 2148058, at *9 (Tex. May 8, 2015), the Supreme Court of Texas addressed interdependent expert testimony, holding that an expert’s opinions are unreliable if they use another expert’s unreliable opinions “to provide a complete factual foundation for” the testifying expert’s theories. Accordingly, the holding in Gharda can be used as another arrow in a litigant’s quiver to attack unreliable opinions.


The case in Gharda concerned a fire at a warehouse where one of the plaintiffs—a chemical company—formulated insecticides and pesticides. To formulate its products, the company used a chemical obtained from the defendants. During a process by which the company melted the defendants’ chemical in an industrial oven for use, a fire ensued that consumed nearly the entire warehouse.

Claiming that the defendants’ chemical caused the fire because it was contaminated, the company and the other plaintiffs sued the defendants for alleged manufacturing defect and negligence, among other claims. At trial, the plaintiffs relied on two fire investigators and two chemists to prove causation. The fire investigators testified that the fire started in the industrial oven where the defendants’ chemical was located, but relied on the chemists to explain how the fire could have started there. The chemists testified that contamination in the chemical had caused the fire.

After the jury returned a verdict against the defendants for more than $8 million, the defendants moved for judgment notwithstanding the verdict and ultimately prevailed because the trial court found that the plaintiffs’ expert testimony was unreliable. The plaintiffs appealed, and the court of appeals reversed in a split decision, at which point the defendants petitioned the Supreme Court of Texas for review.

The Supreme Court of Texas Decision

The Supreme Court of Texas affirmed the trial court’s decision, rejecting all of the experts’ opinions as unreliable. One of the chemists opined that the defendants “possibl[y]” manufactured a contaminated chemical that “could have exploded.”[1] The court deemed that this opinion was unreliable (among other reasons) because (a) expert testimony must be based on reasonable probability, not “mere possibility”; (b) the manufacturing process could have resulted in contamination, but the expert did not establish that it did here; and (c) the expert was unable to quantify the amount of contamination in the chemical at issue and whether that amount was sufficient to cause an explosion.[2]

At trial, the other chemist had testified that contamination caused the chemical to spontaneously combust or be ignited by static electricity. The court rejected this opinion because the chemist did not test, among other things, the amount of contamination in the chemical, at what temperature spontaneous combustion would occur, and whether a static charge could develop in the oven. The court concluded, therefore, that the chemists’ opinions were “the ipse dixit of the expert[s]” and therefore unreliable.[3]

The court also rejected the opinions of the two fire investigators as unreliable because they were dependent on the chemists’ opinions, emphasizing that “interrelated expert testimony cannot be used to form a hybrid for which no single expert can offer support.”[4] According to the court, the two investigators “relied on other experts to provide a complete factual foundation for their origin theories,”[5] but the “factual foundations never materialized because neither chemist provided reliable expert opinion testimony.”[6] The court concluded that the investigators’ testimony should therefore be disregarded.

Because the expert testimony was the only noncircumstantial evidence of causation, the court held that the plaintiffs could not prove causation. The trial court was therefore right to set aside the jury’s $8 million verdict.


Gharda is noteworthy for at least two reasons. First, the Supreme Court of Texas reaffirmed that expert witnesses in Texas cannot base their opinions on assumed facts, speculation, or mere possibility. Gharda will therefore likely be useful for challenging unreliable expert opinions generally. Second, the court rejected interdependent opinion testimony in which an expert relies on another’s unreliable opinions to provide a “complete factual foundation” for his or her own theories.[7] Not surprisingly, a litigant in Texas cannot stack one unreliable expert on another to form a reliable opinion.


If you have any questions or would like more information on the issues discussed in this LawFlash, please contact any of the following Morgan Lewis lawyers:

David J. Levy

[1] Gharda, 2015 WL 2148058, *7-8.

[2] Id.

[3] Id. at *8.

[4] Id. at *9 (internal quotation marks omitted).

[5] Id.

[6] Id.

[7] Id. at *9.