10th Cir.

Mazur v. State Farm Mutual Automobile Insurance Company

April 17, 2026 ·1:23-CV-02618-STV) ·Panel Decision ·Carolyn B. McHugh · By Maria Santos

The Tenth Circuit affirmed a district court ruling denying uninsured motorist coverage to plaintiffs injured in a rollover accident. The court held that the plaintiffs failed to satisfy the causation prong of the Kastner test under Colorado law.

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Background

Plaintiffs Stephanie Mazur and Julia Wunder were injured when Mazur swerved to avoid a pedestrian, William Westuk, who had walked into the travel lane of Interstate Twenty-Five. Westuk was a passenger in an uninsured Subaru that had broken down three hours earlier. The driver, Richard Fralick, had instructed Westuk to stay in the vehicle, but Westuk left against his advice and walked into the southbound lanes. Plaintiffs sought uninsured motorist coverage from State Farm, which denied the claim. The district court granted summary judgment for State Farm, ruling that the plaintiffs were not entitled to coverage under Colorado law.

The court’s reasoning

The court applied the two-part test established by the Colorado Supreme Court in State Farm Mutual Automobile Insurance Company versus Kastner. The court assumed without deciding that the first prong regarding the ‘use’ of the vehicle was met. However, the court concluded that the plaintiffs failed the second prong regarding causation. The court found that Westuk’s independent choice to leave the vehicle and walk into the travel lane, against the driver’s advice and without his knowledge, constituted an independent significant act that interrupted the causal chain between the vehicle’s use and the plaintiffs’ injuries. The court rejected the plaintiffs’ argument that foreseeability of the breakdown and subsequent actions satisfied the causation requirement, noting that the Kastner test requires a direct and inextricable link rather than mere foreseeability.

Plaintiffs’ injuries cannot be considered directly related or inextricably linked to Mr. Fralick’s use of the Subaru when the causal chain between his use of the vehicle and their injuries was thus interrupted by this independent significant act by a third party.

Mazur v. State Farm Mut. Auto. Ins. Co., No. 25-1133, slip op. at 19 (10th Cir. Apr. 17, 2026)

What it means going forward

The decision clarifies that uninsured motorist coverage under Colorado law does not extend to injuries caused by independent actions of a passenger that sever the causal link to the vehicle’s operation, even if the vehicle’s breakdown initiated the sequence of events.

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