Kurt Stuhlmacher v. Home Depot U.S.A., Incorporate, 774 F.3d 405

Kurt Stuhlmacher fell from a four‑legged fiberglass step ladder purchased from Home Depot while working on a roof; he suffered severe personal injuries including Peyronie’s disease.
Post‑accident inspection revealed the right rear spreader bracket rivets had been pulled through the right rear rail and some braces were bent.
Plaintiffs sued Home Depot and ladder manufacturer Tricam Industries for product defect; they retained Dr. Thomas Conry, a mechanical‑engineering accident reconstructionist, to opine that substituted rivets and manufacturing deformation weakened the ladder.
Dr. Conry testified the weakened rivet/bracket connection would have changed ladder stiffness, likely causing Kurt to sense instability and involuntarily shift his weight left as the rivets began to pry through the fiberglass.
The magistrate judge struck Dr. Conry’s causation testimony mid‑trial, concluding it conflicted with Kurt’s testimony that the ladder “suddenly…fell…to the left,” and then entered judgment as a matter of law for defendants because plaintiffs had no remaining causation evidence.
The Seventh Circuit reversed, holding the judge abused his discretion by excluding the expert and impermissibly acting as trier of fact; the jury should have been allowed to weigh the expert’s reconstruction against Kurt’s memory.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether the magistrate properly excluded Dr. Conry’s expert testimony under Daubert (relevance/gatekeeping)	Dr. Conry’s reconstruction was relevant, reliable, and would assist the jury in determining causation; his theory is reconcilable with Kurt’s account	Expert opinion conflicted with plaintiff’s testimony and therefore was irrelevant to causation	Reversed: exclusion was an abuse of discretion; testimony was sufficiently related to the facts to aid the jury
Whether striking the expert required entry of judgment as a matter of law	Without the expert, plaintiffs lacked evidence of proximate cause; exclusion was improper so JMOL cannot stand	Exclusion left plaintiffs with no causation evidence, so JMOL for defendants was proper	Reversed JMOL and remanded for new proceedings; judge improperly supplanted jury’s role

Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993) (trial courts act as gatekeepers to assess reliability and relevance of expert testimony)
Walker v. Soo Line R.R. Co., 208 F.3d 581 (7th Cir. 2000) (standards for admissibility and appellate review of expert testimony)
Smith v. Ford Motor Co., 215 F.3d 713 (7th Cir. 2000) (expert testimony admissible if it will aid the jury; correctness is factual question for jury)
Lauzon v. Senco Prods., 270 F.3d 681 (8th Cir. 2001) (expert opinion admissible where a sufficient nexus exists between expert theory and plaintiff’s account)
Hossack v. Floor Covering Assocs. of Joliet, Inc., 492 F.3d 853 (7th Cir. 2007) (standard of review for JMOL)
Lee v. Smith & Wesson Corp., 760 F.3d 523 (6th Cir. 2014) (parties may prove cases with relevant evidence even if it contradicts witness testimony)