Environmental Engineering Expert’s Failure to Consider Mitigation Efforts Renders His Opinions Unreliable
Posted on August 8, 2025 by Expert Witness Profiler
Plaintiffs Tonya Clayton and Hazel Stroble allege that an automobile assembly plant operated by Defendant FCA US LLC (“FCA”) near their homes in Detroit, Michigan (the “Detroit Plant”) emitted noxious odors into their neighborhood. They said that these odors unreasonably interfere with their ability to use and enjoy the residences that they own and depreciate the values of those residences.
In this putative class action, Clayton and Stroble asserted claims of nuisance and negligence against FCA based on FCA’s operation of the Detroit Plant.
Plaintiffs asked the Court to certify the following class: “All owner-occupants and renters of residential property located, in whole or in part, within one mile (1.0) of [the Detroit Plant], located at 2101 Connor Street/4000 St. Jean Street, Detroit, Michigan from March 1, 2021 to the present.”
FCA filed two motions to exclude the opinions of Plaintiffs’ expert witnesses, Dr. Mark P. Cal and Orell C. Anderson. Plaintiffs relied upon Cal and Anderson
in support of their class certification motion.
Environmental Engineering Expert Witness
Dr. Mark P. Cal obtained a B.S. in Chemical Engineering and a M.S. and Ph.D. in Civil & Environmental Engineering from the University of Illinois at Urbana-Champaign (UIUC). He is currently the Campus Director and Vice President for Academic Affairs and a Professor of Civil and Environmental Engineering at New Mexico State University (NMSU) Alamogordo. For nearly 12 years, he was Chair and Professor in the Department of Civil and Environmental Engineering at New Mexico Tech (NMT).
Cal’s research and consulting experience spans 36-years, and he has worked on projects in the areas of air pollution control, air quality science, atmospheric dispersion modeling (odors, gases and particles), chemical fate and transport, water resources engineering, and heat and mass transfer.
Appraisal and Valuation Expert Witness
Orell C. Anderson is a valuer and expert forensic consultant with extensive experience in appraisal, diminution-in-value and litigation support matters involving commercial, industrial, subdivisions, and vacant land properties, as well as single- and multi-family residences.
He specializes in real property damage economics and property value diminution on a local to global basis and has worked on some of the most notable environmental, social justice, and terrorist cases in recent times.
Discussion by the Court
Mark Cal
Cal did not acknowledge or account for the mitigation efforts that FCA undertook beginning in the fall of 2021
Cal opined that (1) “the entire 1.0-mile proposed class area displayed some level of elevated odor concentrations above [one odor unit per cubic meter]” and (2) “there is clear and convincing evidence that odors were dispersed throughout [the] proposed class area at an odor threshold level that residents would find offensive.”
It is not clear from Cal’s report whether he is offering these opinions with respect to the limited time period for which he had actual sampling data (October and November of 2021) or, alternatively, with respect to the entire time frame covered by Plaintiffs’ proposed class definition (March of 2021 to the present).
To begin with, Cal did not acknowledge or account for certain mitigation efforts that FCA undertook beginning in the fall of 2021. According to the Court, his failure to consider those mitigation efforts, and to explain what effect, if any, those efforts had on the odor unit level in the proposed class area during the class period (March 1, 2021, through the present), rendered his opinions unreliable.
Next, if Cal’s opinion is limited to the time period for which he had sampling data, then it must be excluded because it is not an appropriate fit for the proposed class. As noted above, Plaintiffs are seeking to certify a class that spans from March 1, 2021, to the present. But an opinion covering only a small fraction of that period – i.e., the two-month period in the fall of 2021 for which Cal had sampling data – says little, if anything, about whether the criteria for class certification are satisfied for the entire proposed class period.
There is no reliable basis for Cal’s opinion that all of the members of the proposed class would find the odor level emitted from the Detroit Plant to be offensive
Cal bases that opinion solely on the fact that the odor emanating from the Detroit Plant was measured at one odor unit per cubic meter. But as Cal acknowledged, at that level, only “50 percent of the people” would even be able to “smell” the odor.
The Court ruled that Cal has not sufficiently explained how an odor that only 50 percent of people can even detect could reasonably be considered offensive to the entire proposed class. Moreover, his opinion that the class members would find the odor offensive because it measured one odor unit per cubic meter is at odds with his acknowledgment that five odor units per cubic meter, not one, is “generally” the “threshold level that residents would find offensive.”
Orell Anderson
The Court next turns to Anderson’s opinion that he could develop a reliable model to determine the economic damages suffered by the proposed class members.
Plaintiffs sought to certify a class that includes both “owner-occupants and renters” in the class area. But Anderson’s proposed model does not apply to renters. Instead, he intended to measure only the diminution in property values caused by the odors emanating from the Detroit Plant, and it is only property owners that could have suffered such a potential diminution.
That Anderson’s proposed model does not apply to renters is a significant problem because FCA has presented evidence that approximately 45% of the proposed class members are renters, not owners. Because Anderson’s proposed model did not apply to the many renters in the proposed class, the Court held that it is not a proper fit for that class.
Held
The Court granted FCA’s motions to exclude Plaintiffs’ expert witnesses, Dr. Mark Cal and Orell C. Anderson.
Key Takeaways:
- To be clear, Cal certainly was not required to agree with FCA that its mitigation efforts meaningfully decreased the odors emitted from the Detroit Plant. But to be reliable, his analysis had to at least acknowledge those efforts and explain how, if at all, those efforts impacted the odor levels and his analysis.
- Anderson’s proposed model has a major flaw—it doesn’t apply to renters. This is a serious issue because FCA has shown that about 45% of the proposed class members are renters, not owners.
Case Details:
| Case Caption: | Clayton V. FCA US LLC |
| Docket Number: | 4:21cv12995 |
| Court Name: | United States District Court, Michigan Eastern |
| Order Date: | August 07, 2025 |
