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Mold Litigation: Expert Testimony Required to Prove Causation

Kent Holland | April 1, 2006

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Petri plate containing mold

Due to lack of expert testimony concerning causation, a federal district court in Texas dismissed a suit by a homeowner alleging that a leaking sewer pipe in a basement crawl space caused mold to grow throughout the house. No previous Texas cases have dealt specifically with whether expert testimony was required to prove the causation of the mold. The court, therefore, looked to other Texas cases holding expert testimony is required to establish negligence when issues and standards are not familiar to the ordinary person, and to cases holding expert testimony is required to establish causation of injury from toxic substances.

In E. Lee Qualls v. State Farm Lloyds, 226 F.R.D 551, 2005 U.S. Dist LEXIS 5049 (2005), the U.S. District Court for the Northern District of Texas granted summary judgment in favor of the insurance company (State Farm) in a claim under a homeowners insurance policy brought by homeowner (Qualls) alleging mold property damage in their home. The first issue considered by the court was the failure of the Qualls to designate expert witnesses in a timely manner. The plaintiff thought it could proceed with its case based on fact witnesses alone. They did not designate any expert on causation.

The court concluded that due to the lack of expert testimony, summary judgment would be appropriate. The plaintiff then filed a motion for leave to designate experts.

The court denied the motion for leave to designate experts because discovery (including depositions) had already been completed, and it was the eve of trial before the plaintiffs belatedly sought to designate experts. This would have caused prejudice to the defendant in litigating the case.

Having denied the motion for leave to designate experts and present expert testimony, the court next analyzed whether the case could go forward to a trial without expert testimony or whether it would have to be dismissed as a matter of law.

The federal court naturally looked to the law of the state of Texas to determine what was required in the way of expert testimony. Under Texas law, expert testimony is not required in those cases in which general experience and common sense will enable a layman to determine with reasonable probability, the causal relationship between the event and the condition.

The U.S. District Court looked at how Texas Supreme Court decisions have addressed the need for expert testimony in the context of standard of care in a negligence case. The Texas courts "have considered whether conduct at issue involves the use of specialized equipment and techniques unfamiliar to the ordinary person."

The District Court looked at how the Texas courts deal with proof of medical causation. What it found was that, "Numerous Texas cases have held that expert testimony is required to establish causation of injury from exposure to toxic substances." No Texas case was found to specifically address proof of causation with regard to mold.

The court also looked to case law outside the state to determine how other courts have addressed the situation and was so impressed with a factually similar case and decision written by the U.S. District Court for the Eastern District of Pennsylvania (Kermmerer v. State Farm Ins., 2004) that it quoted from the decision at length. That case involved a leaking toilet which a homeowner alleged caused mold infestation to accelerate. The defendant in that case argued that the plaintiff lacked requisite formal training or education required to render an opinion as to the cause of infestation.

The Pennsylvania court concluded the following:

To establish such an element of complex causation, however, Plaintiff must provide evidence beyond lay opinions. In a case involving complex issues of causation not readily apparent to the fact finder, plaintiff must present admissible expert testimony to carry her burden. The report provided by Plaintiff's expert provides conclusions as to the presence, levels, and likely health hazards of mold cultures in the house. It does not speak to the cause of the mold infestation. If the expert testimony cannot support both general and specific causation, summary judgment for the defendant must be granted. Opinions merely expressing "possibilities" do not suffice to support the admissibility of expert testimony; an expert must supply more than a bottom line to be of value to the judicial process.

Turning to the facts of the instant case, the court in Texas found that the Texas case law concerning expert testimony is consistent with the above-quoted Pennsylvania case. The court, therefore, found Kemmerer to be persuasive authority that expert testimony is required in this case:

Although it may be within general experience that water can cause mold, it is not within general experience that a buried sewer pipe that does not leak under normal flow conditions could cause mold over an extended distance throughout the house.

The court also noted that "When there is, as here, expert testimony that another source is a likely cause of the mold, lay testimony is not adequate to rule out that alternate cause." Although the court noted that "some circumstances may be clear enough to fall within the common experience of jurors" and that it would not hold that expert testimony is always required to show the cause of mold, such expert testimony was required in this case based upon the facts. For these reasons, the court granted summary judgment against the homeowner and in favor of the insurance company.


In mold cases that allege bodily injury, a plaintiff may be required to prove through expert testimony not only what caused the mold growth, but also that the mold caused the alleged bodily injuries. This can be a difficult matter to prove, and summary judgments are not uncommon. As this Texas case demonstrates, expert testimony is also required to prove causation of property damages in cases involving mold.

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