Restatement Second of Torts Section 388
Section 388 of the Restatement Second of Torts states: "One who supplies directly or through a third person a chattel for another to use is subject to liability to those whom the supplier should expect to use the chattel with the consent of the other or to be endangered by its probable use, for physical harm caused by the use of the chattel in the manner for which and by a person for whose use it is supplied, if the supplier (a) knows or has reason to know that the chattel is or is likely to be dangerous for the use for which it is supplied, and (b) has no reason to believe that those for whose use the chattel is supplied will realize its dangerous condition, and (c) fails to exercise reasonable care to inform them of its dangerous condition or of the facts which make it likely to be dangerous."
In Johnson v. American Standard, Inc. (2008) 43 Cal.4th 56, the California Supreme Court recognized the defense based on comment k accompanying section 388 of the Restatement Second of Torts.
There, a trained and certified heating, ventilation, and air conditioning (HVAC) technician suffered injuries due to his repeated exposure to R-22, a refrigerant. (Johnson, supra, at pp. 61-62.) The technician asserted claims for personal injury against several manufacturers and suppliers, alleging that they had failed to warn him of the dangers of R-22. (Id. at p. 62.) After one of the defendants obtained summary judgment on the ground that the technician was aware of the risks of R-22, the Supreme Court held that the sophisticated user defense, as reflected in comment k to section 338, was applicable in California. (Johnson, supra, at p. 61.)
In so concluding, the court stated:
"A manufacturer is not liable to a sophisticated user of its product for failure to warn of a risk, harm, or danger, if the sophisticated user knew or should have known of that risk, harm, or danger. It would be nearly impossible for a manufacturer to predict or determine whether a given user or member of the sophisticated group actually has knowledge of the dangers because of the infinite number of user idiosyncrasies. ... However, individuals who represent that they are trained or are members of a sophisticated group of users are saying to the world that they possess the level of knowledge and skill associated with that class. If they do not actually possess that knowledge and skill, that fact should not give rise to liability on the part of the manufacturer. Under the 'should have known' standard there will be some users who were actually unaware of the dangers. ... Nonetheless, even if a user was truly unaware of a product's hazards, that fact is irrelevant if the danger was objectively obvious. Thus, under the sophisticated user defense, the inquiry focuses on whether the plaintiff knew, or should have known, of the particular risk of harm from the product giving rise to the injury." (Johnson, supra, 43 Cal.4th at p. 71.)