S. Gopalratnam v. ABC Insurance Company, 877 F.3d 771

In June 2010 a fire in plaintiffs’ home killed their son; investigators recovered an HP laptop and three 18650 lithium‑ion cells from the mattress/debris.
Plaintiffs sued HP (and third‑party defendants DynaPack and Samsung) claiming a defective battery cell caused thermal runaway and ignited bedding.
Plaintiffs relied solely on two experts: Dr. Daniel Doughty (battery safety) who concluded one cell (Cell A) suffered an internal short/thermal runaway caused by a manufacturing defect or safety‑circuit failure; and Michael Hill, a fire investigator who concluded the laptop battery was the most probable ignition source.
Defendants moved to exclude both experts under Fed. R. Evid. 702/Daubert; the district court found both qualified but excluded their opinions as unreliable and granted summary judgment for defendants.
On appeal the Seventh Circuit reviewed the district court’s Daubert analysis for abuse of discretion and affirmed the exclusion and summary judgment.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether Doughty’s causation opinion (internal fault/thermal runaway due to manufacturing defect or control failure) was admissible under Rule 702/Daubert	Doughty: Cell A’s deformation, ejection of contents, and being a projectile show a distinct failure mechanism inconsistent with uniform external‑fire effects; thus an internal fault triggered thermal runaway	Defs: Differential cell outcomes are consistent with stochastic/random responses to external fire; Doughty’s premise and literature support are unreliable and speculative	Court: Excluded — Doughty’s central premise (cells should respond uniformly to external fire) is contradicted by the literature and he failed to bridge the analytic gap or account for alternative explanations; his attribution to a manufacturing defect/control failure was speculative
Admissibility of Hill’s causation opinion, which relied on Doughty	Hill: He conducted origin work and identified the laptop battery as most probable ignition source; relied on Doughty for technical battery causation	Defs: Hill’s battery causation depends on Doughty’s excluded methodology; Hill lacks independent battery expertise	Court: Excluded — Hill’s causation opinion largely rests on Doughty; Rule 703 does not rescue opinions built on another expert’s unreliable methodology; without these experts plaintiffs cannot prove causation, so summary judgment appropriate

Daubert v. Merrell Dow Pharm., 509 U.S. 579 (gatekeeper role under Rule 702 for expert testimony)
Kumho Tire Co. v. Carmichael, 526 U.S. 137 (Daubert applies to technical and other specialized expert testimony)
Krik v. Exxon Mobil Corp., 870 F.3d 669 (7th Cir. 2017) (discussing Rule 702/Daubert framework and standards of review)
Manpower, Inc. v. Ins. Co. of Pa., 732 F.3d 796 (7th Cir. 2013) (methodology v. conclusions; need for connection between data and opinion)
Stollings v. Ryobi Techs., Inc., 725 F.3d 753 (7th Cir. 2013) (district court gatekeeping focuses on methodology and data sufficiency)