INTRODUCTION
For over twenty years, I have exposed my students to the conceptual vacuity of the ‘substantial factor test’ for factual (and, for that matter, proximate) causation. Most torts scholars I know do the same. I explain that although many jurisdictions still purport to use a substantial factor test, even such jurisdictions typically apply the test as a combination of the but-for test, the overdetermined cause rule, and a couple of evidentiary mechanisms that aid plaintiffs in cases in which the evidence to prove causation is thin or unavailable. I go so far as to exhort my students that: ‘The words “substantial factor” are useless and should not appear on your exams!’ And yet inevitably, each year several students claim that the misdeeds of my exam’s hapless defendants were a substantial factor in causing the plaintiff’s harm. Sigh …
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W Jonathan Cardi, Goodbye Substantial Factor, Hello Doull v. Foster!, Journal of Tort Law, volume 16, issue 1. Published by De Gruyter 29 May 2023.
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