The standard of reasonable care is the most important example of a substantive tort obligation that is largely determined by folk law or the understanding that jurors as lay individuals have about the legal obligation. In order to be adequately determinate, the folk law of reasonable care must be based on a widely shared metanorm that jurors use to evaluate socially acceptable behavior. Studies of jury decision-making in tort cases assume that there is such a metanorm without identifying it. These studies, like torts scholarship more generally, have not accounted for the substantial body of evidence showing that individuals are guided by a metanorm of reciprocity that is highly relevant to the resolution of negligence cases. By applying this metanorm to the case at hand, jurors enforce behavioral obligations that map into the modern tort rules of negligence and strict liability. A metanorm of reciprocity quite plausibly defines folk tort law, although it is a separate question why the legal system chooses to enforce this social norm. Folk tort law is not fully capable of answering this question, but as an important component of modern tort law, it should be accounted for by any persuasive interpretation of the practice.
Geistfeld, Mark, Folk Tort Law (August 2019). Handbook of Private Law Theories (Hanoch Dagan and Benjamin Zipursky eds, Edward Elgar Press 2020, forthcoming); NYU School of Law, Public Law Research Paper No 19-37.