Testimony of Automotive Engineering Expert Witness Limited for Lacking Evidence beyond his Subjective Opinion

Testimony of Automotive Engineering Expert Witness Limited for Lacking Evidence beyond his Subjective Opinion

This case arises out of Plaintiff Mark Riley’s claim that General Motors breached a contract and express warranty to repair his 2017 GMC Acadia vehicle (“Subject Vehicle”) in a reasonable time. The 3-year/36,000-mile limited warranty that accompanied the Subject Vehicle (“Limited Warranty”) provided for repair of covered defects occurring during the warranty period, subject to certain terms, conditions and limitations, including that the owner or lessee take the vehicle to a GM authorized dealer during the warranty period and allow reasonable time for a repair. Plaintiff contended that shortly after he purchased the Subject Vehicle, he experienced a condition where, to turn off the vehicle’s accessory mode, he was required to take certain additional steps such as wiggling the shifter and moving the shifter in and out of park (the “STP condition”).

The STP condition occurred in a small minority of proposed class vehicles, and even then, manifested at different rates across vehicle models, which used shifter assemblies integrated into the different vehicles in different ways.

Plaintiff disclosed the Report and Expert Opinion of Darren Manzari on February 3, 2023 (the “Manzari Rpt.”). Manzari is Plaintiff’s sole expert in this case. Among other things, Manzari opined on whether certain shifter assemblies included in Class Vehicles were “defective.”

GM argued that this Court should exclude the testimony and opinions of Plaintiff’s expert, Darren Manzari, due to (1) Manzari’s lack of relevant “knowledge, skills, or experience” as to economics, damages, and safety and (2) the opinions’ failure to meet Rule 702 standards on account of insufficient factual underpinnings and inappropriate speculation or conclusions.

Automotive Engineering Expert Witness

Darren Manzari has worked in the automotive industry for 35 years. He graduated from Farmingdale University in 1986 with AAS Degree in Automotive Engineering. In 1998, he began a training and consulting business, ATC.

Through ATC, he provided automotive technical training and consulting to Colleges, OEM Dealerships and aftermarket automotive facilities, in New York, Massachusetts, Maryland, North Carolina, South Carolina, Georgia and Florida.

Discussion by the Court

Manzari’s diverse career and training spans different facets of the automotive industry over thirty-five years. Manzari applied this experience in his expert report, tailoring his opinions and conclusions based on a variety of relevant documents, including numerous GM statements, reports, and service bulletins to dealers, as well as documents produced by GM itself, including Plaintiffs’ vehicle service records. The Court agreed with prior evaluations of Manzari’s credentials and methodology of applying “his knowledge and experience to a review of an extensive list of relevant documents” as “sufficient to satisfy the Court’s gatekeeping function.”

Manzari’s opinions that GM took too long to diagnose and identify a repair for the Shifter Defect, and failed to cure the Shifter Defect

GM asserted that these opinions lacked scientific analysis, and instead “simply summarized GM testimony, improperly couched as his opinion,” so such opinions should be inadmissible as unreliable.

The Court found that these opinions were a result of Manzari’s interpretation of record evidence based on his relevant and qualified experience and knowledge.

Manzari’s opinions that Class Vehicles suffer from a Shifter Defect that GM did not repair during the Warranty Period

GM argued that such opinions lacked independent analysis, were unreliable, and Manzari opined on areas that were within the province of the judge (legal conclusions) and the jury (factual questions).

However, Manzari examined various documents pertaining to Plaintiff’s vehicle—including (1) GM’s warranty history for Plaintiff’s vehicle; (2) Plaintiff’s vehicle purchase records; and (3) the dealership service records for the vehicle owned by Plaintiff—as well as GM’s own documents in this action.

The Court found these opinions to be the result of a reliable methodology applied to a sufficient set of facts.

The opinions involved application of his knowledge and expertise in concluding that certain repair attempts did not actually repair the defect.

Manzari’s opinion that Class Vehicles are unsafe to drive

GM claimed that such an opinion was excludable because Manzari is not a vehicle safety expert. Manzari’s opinion that the Class Vehicles were unsafe to drive was an “ordinary purpose” opinion.

The Court held that Manzari is qualified by virtue of his knowledge and experience to testify on the functioning of the vehicles.

Manzari’s opinions that the Shifter Defect would have impacted consumers’ purchasing decisions and does impact the value of the Class Vehicles due to the cost of repair

GM objected to the “anecdotal” nature of Manzari’s opinions regarding any alleged reduction in value and any resulting consumer behaviors.

The Court held that cost of repair is the appropriate calculation for diminution in value damages, as Manzari noted, and the repair cost was in part based on GM’s records. Manzari’s citations to evidence in the record in coming to the precise number were reliable.

And, considering GM itself fronted the cost to fix this issue during the warranty period, it was reasonable to conclude that such an issue impacted the Class Vehicles’ value.

However, in concluding that “most consumers would not have purchased the Class Vehicles, or would have paid substantially less, had the problem been known to them,” Manzari started to depart from the province of what this Court viewed as his expertise, instead veering into consumer demands, with more support.

The Court held that Manzari’s report lacked evidence of “consumer reactions” or evidence beyond “his subjective opinion.”

The admissibility of Plaintiff’s only expert bore on both Defendant’s motion for summary judgment and Plaintiff’s motion for class certification. Plaintiff’s motion for class certification was granted while Defendant’s motion for summary judgment was granted in part and denied in part.


The Court granted in part and denied in part GM’s motion to exclude Darren Manzari’s testimony and opinions.

Key Takeaways:

  1. Expertise and Methodology: Manzari’s diverse career and training in the automotive industry provided a strong foundation for his expert opinions. The Court acknowledged his expertise and methodology in reviewing relevant documents and applying his knowledge and experience to reach conclusions.
  2. Reliability of Opinions: Despite GM’s objections regarding the lack of scientific analysis and independent analysis in Manzari’s opinions, the Court found them to be reliable interpretations of record evidence based on his relevant experience and knowledge.
  3. Qualifications for Testifying: The Court upheld Manzari’s qualifications to testify on vehicle functioning.

Case Details:

Case Caption: Riley V. General Motors LLC
Docket Number:2:21cv924
Court:United States District Court, Ohio Southern
Order Date:March 25, 2024


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