Probability Theory Meets Res Ipsa Loquitur

This Article uses probability theory normatively in an effort to clarify one aspect of the famous tort doctrine known as res ipsa loquitur. It does not urge that jurors be instructed in probability theory or be equipped with microprocessors. Rather, it seeks an accurate statement of the res ipsa doctrine in ordinary language. In particular, this Article will show that the conventional formulation of the doctrine is misleading at best, and should be replaced with a more careful statement of the conditions warranting the res ipsa inference. To this end, Section I briefly surveys the legal doctrine, or, more precisely, the aspect of the doctrine that will be criticized. Section II develops a mathematical apparatus and uses it to expose the weakness in the current version of res ipsa loquitur. Finally, Section ID summarizes and elaborates the conclusions reached-in Section II – conclusions that suggest which cases should reach a jury and what instructions the jury should receive.