Copy of Third Circuit Revives Sig Sauer P320 Injury Lawsuit Despite Expert Testimony Exclusion

Background: Federal Agent Sues Over Accidental Discharge of Sig Sauer P320

In Slatowski v. Sig Sauer, Inc., the U.S. Court of Appeals for the Third Circuit ruled that a lawsuit involving a defective gun design may proceed to trial—even though the plaintiff’s expert testimony on causation was excluded by the lower court .

The case stems from a 2018 incident involving Keith Slatowski, a federal immigration agent and former Marine, who claims his Sig Sauer P320 pistol accidentally discharged while holstered during a training session—without his finger on the trigger. The bullet struck his leg, prompting a personal injury lawsuit against Sig Sauer for an alleged design defect.

The Defect Allegations: No External Safety + Sensitive Trigger

Slatowski contends that the P320’s lack of an external safety and sensitive single-action trigger made it prone to accidental discharge. The gun has two internal safeties but no thumb safety or grip safety, unlike versions issued to the military .

He argued that a “tabbed trigger”—which requires a direct, deliberate press—would have reduced the risk of accidental firing caused by debris or holster contact.

📸 The court’s opinion includes a diagram of the P320’s internal safety system on page 2, explaining how the striker, sear, and safety lock interact.

Expert Testimony Thrown Out—But the Lawsuit Survives

The District Court had excluded testimony from both of Slatowski’s experts: a gunsmith and an ergonomics specialist. While the court allowed their opinions on the gun’s defective design, it ruled that neither expert could reliably opine on the cause of the accidental firing since they failed to simulate the incident or test the interaction between the gun and the holster .

This led the District Court to grant summary judgment in favor of Sig Sauer, believing the jury couldn’t determine causation without expert guidance.

However, the Third Circuit reversed that decision, finding that the jury could draw its own conclusions from eyewitness testimony and physical evidence, such as the weapon and holster, especially with expert background on the gun’s design .

Court’s Reasoning: Juries Can Handle This Without a Causation Expert

Judge Bibas, writing for the panel, emphasized that Pennsylvania law doesn’t require expert testimony when the issue is within a juror’s common understanding. Since the experts could explain how the P320 operates, the jury can evaluate whether Slatowski’s story holds up—without needing scientific proof of exactly how the gun discharged .

The court contrasted this case with others involving mysterious mechanical failures, where expert insight is essential. Here, the facts—including Slatowski’s claim that he didn’t touch the trigger—are sufficiently tangible for a jury to assess.

National Impact: A Split Among Circuits on P320 Lawsuits

This decision aligns the Third Circuit with the Sixth Circuit (see Davis v. Sig Sauer), both of which have allowed P320 defect lawsuits to proceed without expert causation testimony. It diverges from the Tenth Circuit, which recently ruled otherwise based on a different factual record .

What This Means for Gun Owners and Manufacturers

The ruling is a significant win for plaintiffs in product liability cases involving firearms. It lowers the bar for surviving summary judgment, particularly when plaintiffs have first-hand accounts and basic physical evidence—even if expert causation testimony is excluded.

It also places renewed scrutiny on Sig Sauer’s P320 model, which has faced numerous lawsuits for accidental discharges—some resulting in settlements or safety upgrades. Gun owners, law enforcement agencies, and firearm safety advocates should follow these developments closely.

Takeaways

• Expert causation testimony is not always required in defective firearm cases under Pennsylvania law.

• Eyewitness accounts and physical evidence can be sufficient to reach a jury.

• Plaintiffs may argue design defect based on lack of external safety mechanisms.

• The case will now proceed to trial following the reversal of summary judgment.