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Environmental Law Blog

The Importance of Avoiding Net Opinions in Environmental Cleanup Disputes

November 9, 2021

The Appellate Division’s unpublished decision in Meyer v. Constantinou, decided earlier this year, affirmed the exclusion of the testimony of an environmental expert as a “net opinion” for disregarding key facts and data without appropriate reasoning and justification.

Understanding the Admissibility of an Expert’s Opinion in New Jersey Courts

Rule 703 of the New Jersey Rules of Evidence provides that an expert must base his or her opinion on facts or data presented at or before trial. The corollary to Rule 703 is the “net opinion” rule, which requires an expert to explain why and how an event took place rather than merely provide a conclusion or “net opinion.” See Townsend v. Pierre, 221 N.J. 36, 53-54 (2015); Polzo v. Cnty. of Essex, 196 N.J. 569, 583 (2008); State v. Townsend, 186 N.J. 473, 494 (2006). An expert’s opinion becomes inadmissible as a “net opinion” if it is based on speculation, unquantified possibilities, or fails to make the connection between the incident and the resulting damages.

Federal courts use a formalized standard known as the “Daubert factors” as a means to determine whether or not expert testimony should be admissible at trial. In New Jersey, the Daubert factors are used as a “helpful - but not necessary or definitive - guide” for courts to consider when determining whether or not the expert opinion  is admissible. In re Accutane Litigation, 234 N.J. 340 (2018). The admission or exclusion of evidence, as well as the determination of an expert’s credibility, ultimately lies in the sound discretion of the trial court.

Expert’s (In)Action in Environmental Cleanup

The opinion in Meyer v. Constantinou, No. A-1793-18, 2021 WL 1499851 (N.J. Super. Ct. App. Div. Apr. 16, 2021), while unpublished, sheds light on the problems that arise when an expert offers an unsupported, or net, opinion in an environmental cleanup dispute.

In Meyer, a gas station/auto repair shop discovered PCE contamination in the soil on its property when it was remediating chemicals that had leaked from its underground storage tanks. The gas station then initiated legal action against a dry cleaning facility located at a nearby shopping center. At trial, the gas station’s expert contended that the PCE contamination migrated downhill from the dry cleaner onto the gas station property. The court held the gas station failed to establish liability and ruled in favor of the defendants, in part because the gas station’s expert provided an inadmissible “net opinion” due to his failure to sufficiently support or explain his methodology.

Missing Samples and Making Assumptions - When the Facts and Numbers Don’t Add Up

On appeal, the Appellate Division affirmed the trial court’s view that the gas station’s expert had rendered an inadmissible “net opinion.” The court pointed out that the expert relied on a number of unfounded “facts” about the gas station property to support his causation opinion.  For example, the expert assumed the PCE stemmed from the nearby dry cleaners because the gas station/auto shop did not use chlorinated solvents in its operations. Yet, a Preliminary Assessment of the contaminated property was never conducted, the prior contents of the waste oil tank and use of the tank by the former owners of the gas station were never confirmed, and the expert never validated the auto shop’s claim that it never used PCE. Similarly, the expert failed to provide sufficient objective data, such as the degree of slope and an assessment of the exact relative topographies of the two properties, to support his theory that rainwater carried PCE downhill from the dry-cleaners onto the gas station. The basis of the expert’s opinion on this point was limited to a single visual observation.

The expert also relied for his causation opinion on soil samples taken from the two properties, but the sampling data did not support his primary reason that the PCE came from the dry cleaners. That is, the expert opined that his isopleth map (a map that uses lines or colors to indicate areas with similar meteorological features) supported the opinion that PCE concentrations decreased as they moved closer to the gas station, explaining that the declining PCE gradients matched the  topography. Yet, the expert did not consider the results of sampling taken from the excavation of the waste oil tank located only several feet from the auto shop building, which detected a substantial amount of PCE, and he acknowledged that if he had included the additional sample in his analysis, the isopleth map he drew would have been completely different.

Finally, the expert made statements about the dry cleaning operations that proved to be unsubstantiated, and he acknowledged he did not know how or when a discharge or spill occurred at that facility. The expert also assumed that the dry cleaners obtained a new dry-cleaning machine around the time of the discovery of the PCE contamination on the auto shop property, and opined that the new equipment was substituted for the prior machine due to the discharges of PCE. Yet, the facts revealed the dry cleaning machine was actually replaced many years after the PCE was first detected at the gas station/auto repair property. The expert had never inspected the dry cleaning equipment, and had never visited the dry cleaners except as a patron. Thus, the Appellate Division concluded that the expert’s opinion relating to the dry cleaning operations was speculative at best.

Ultimately, the Appellate Division affirmed the decision of the trial court that the expert’s opinion was an inadmissible “net opinion,” and it upheld the trial court’s judgment in favor of the defendants.

The Importance of a Good Expert

Meyer represents an important reminder that environmental consultants employed as experts in New Jersey courts must be able to apply their expertise to all the relevant evidence, and be able to justify the reliability of their methodology. Absent the clarity that comes though appropriate data, evidence, and methods that inform the conclusions, it is likely that an expert opinion will be excluded as a net opinion.

For more information, please contact the author Holli B. Packer at or any attorney in our Environmental Practice Group.

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