The saga over the illegality defense in Kansas appears to have run its course, and as in previous chapters, the defense has prevailed.  The Tenth Circuit has ruled that the defense of illegality exists under Kansas law and that it applies to product liability claims.  As we reported here and here, this is the first case applying illegality (aka in pari delicto) as a defense to product liability claims under Kansas law, and the Tenth Circuit ruling is the first appellate opinion to so hold.

To recap, the decedent in Messerli v. AW Distributing, Inc., No. 23-3241, 2025 WL 2525275 (10th Cir. Sept. 3, 2025) (to be published), sadly passed away allegedly as a result of inhaling intoxicating fumes (or “huffing”) from computer dusters, those cans of compressed air you use to blow away dust.  As we wrote here, a federal district court in Kansas granted a motion to dismiss on the basis that the decedent had engaged in illegal conduct, which supported a complete defense.  That was because Kansas’s illegality defense bars claims arising from a plaintiff’s illegal conduct, and huffing is a crime in Kansas under laws against “the unlawful abuse of toxic vapors.”

The Tenth Circuit affirmed, noting at the outset that Kansas has outlawed toxic vapor abuse for good reason, citing the addictive and dangerous nature of certain inhalants and the multiple emergency room visits associated with them. 

In coming to its conclusion, the Tenth Circuit’s reasoning was threefold.  First, the court held that the illegality defense exists under Kansas common law that that the Kansas Product Liability Act did not abrogate it.  The KPLA merges all product liability theories into a single product liability claim, but where the Act is silent, common law fills in the gaps.  The KPLA did not expressly abrogate the illegality defense, and multiple recent Kansas cases confirm that the illegality defense is still available under the common law in tort actions.  The same is true in multiple other states.

Second, Kansas’s adoption of comparative negligence in 1974 did not overrule the illegality defense, either.  On this point, the plaintiff argued that the decedent’s illegal acts should not bar recovery completely, but should reduce the recovery by an amount to be determined by a jury.  The Tenth Circuit, however, rejected this argument on the basis that Kansas courts have continued to apply the illegality defense since the legislature adopted comparative fault.  Moreover, and we think more importantly, comparative fault and illegality are horses of a different color.  Unlike comparative fault, the illegality defense does not aim to apportion fault, but instead prevents injured parties from benefiting from their own illegal behavior.  This is a policy choice.  The Restatement (Second) of Torts recognized that “the public policy behind this rule is that a court should not lend its aid to a [person] who founds [a] cause of action upon an immoral or illegal act.”  Messerli, at *7.  And the Tenth Circuit agreed with other courts holding that plaintiffs should not be compensated for injuries that “involve a substantial violation of law.”  Id. 

Third, the Tenth Circuit affirmed the district court’s Erie determination that the Kansas Supreme Court would apply the illegality defense in product liability cases.  The Kansas Supreme Court has long endorsed a preference that juries allocate fault based on “comparative degrees of causation.”  Id. at *8.  The illegality defense, however, is different because

the policy argument behind the illegality defense is not based on allocating fault, but on the principle that the courts should refuse to allow a plaintiff to benefit from his own illegal act.  The degree of the injured party’s culpability is not at issue.  We are concerned only with whether we should aid a plaintiff who violated the law. 

Id.  The key is that Kansas common law, like the law other states, has always applied the illegality defense for reasons separate and independent from contributory negligence and comparative fault.  As a result, the defense applies to tort claims generally and likewise to product liability claims under the KPLA. 

From there it was a short path to affirming the dismissal.  The complaint alleged that the decedent huffed dusters and that toxic vapor intoxication caused his death.  Because the complaint squarely alleged that illegal acts allegedly caused the death, the illegality defense barred the plaintiff’s claims. 

The Tenth Circuit’s opinion is useful not only because it is the first of its kind, but also because of the clarity of its reasoning.  A plaintiff’s product misuse is one thing; a plaintiff’s attempt to base a civil action on his or her own illegal conduct is quite another.  File this opinion away for future use. 

Thanks to Scott Kaiser, Stephen Nichols, and Holly Pauling Smith at Shook Hardy for bringing this opinion to our attention and for attaining this result.