On Sept. 30, 2024, the U.S. District Court for the Northern District of Indiana released an opinion and order excluding the opinions of a proposed lithium-ion battery expert. The now dismissed case, American Home Assurance Company v. Makita Corporation of America, stemmed from a fire at a “tow-behind trailer” manufacturing facility in Elkhart, Indiana. According to American Home Assurance Company’s complaint, a lithium-ion battery used to power a drill failed and caught fire. The fire then spread throughout the facility and caused significant damage. The facility owner subsequently made a claim under its insurance policy, and American pursued a subrogation action against the battery and power drill manufacturers, among others. Notably, American alleged a defect in the lithium-ion battery’s manufacture and design. As a result, American’s complaint brought several claims for strict product liability under the Indiana Product Liability Act.
The power drill manufacturer eventually sought to exclude testimony from American’s proposed battery expert, who possessed more than 43 years’ experience in the industry. The expert offered two opinions: (1) that the power drill’s battery failed and likely caused the fire, and (2) that the poor design of the battery’s management system caused its failure when its cell became unstable under normal intended use.
To reach those opinions, American’s battery expert visually inspected 80 battery cells that remained after the fire. In this nondestructive inspection, American’s battery expert segregated the cells that suffered an apparent “fire attack” from those that exhibited significantly less damage. He also considered cells with visually “bulbous” negative ends or elongated crimps to be candidates for further inspection. According to the expert, a cell with a “grossly distorted” negative end was likely a fire-attacked cell, though a “slightly rounded” one might still be causative and necessitate further analysis.
This process, which lacked any peer-reviewed support, yielded 20 battery cells for x-rays and further analysis. But American’s battery expert did not preserve the x-rays or document his examination of the x-rays. He also conducted his analysis without either the power drill manufacturer or battery manufacturer present.
The expert subsequently attempted to determine whether the 20 battery cells displayed signs of venting and internal damage. As part of this process, the expert looked for melting on external wrapping and wrinkling to determine whether damage to a cell stemmed from an external fire. He determined that these features revealed that the cell was attacked by fire, rather than being the cause of it. In contrast, the expert believed that the displacement of the battery cell’s core to the two ends of the cell (i.e., pushed in paths) indicated that the cell failed or shorted. The battery expert later performed CT scans on four of the 20 selected cells.
The expert eventually identified one battery cell as the probable cause of the fire. He did so because it lacked significant external damage compared to all other cells involved in the fire, possessed a slightly rounded negative end, and possessed internal damage at the negative end of the cell.
The court concluded that the testing method utilized by American’s battery expert was unreliable, untested, and dependent on subjective and imprecise criteria. American never explained how its expert’s subjective and imprecise selection criteria — “which may show one thing or indeed the opposite thing” — can reliably support his decision to subject only 20 battery cells to x-ray analysis. The court also voiced concerns that the expert failed to preserve his work at that stage. According to the court, such images are crucial in determining the sequence of a thermal runaway event and developing an opinion about a cause for a battery cell’s failure. For those reasons and others, the court excluded American’s battery expert’s opinions. The parties filed a stipulation of dismissal with prejudice 23 days later.
The court’s opinion and order represent a warning to all parties involved in litigation stemming from alleged lithium-ion battery defects. Expert testimony is critical, but parties should be mindful that scientific testimony must be based on reliable, accepted principles and methods. Parties should also be transparent when testing or otherwise manipulating recovered artifacts and be mindful that “opinion based on unsubstantiated and undocumented information is the antithesis of … scientifically reliable expert opinion.”