If R3 is adopted it would mark a significant change and require acclimation to the nomenclature used to present the causation question to the jury. See Weigand, Duty, Causation and Palsgraf: Massachusetts and the Restatement (Third) of Torts, 96 Mass. L. Rev. 55 (2015). R3 arguably provides a more precise approach to causation including providing a clearer demarcation between the factual and policy constituents of causation. R3 is otherwise adamant that the use of substantial factor is concerning and leads to misuse and misunderstanding including the potential to impermissibly heighten or lessen the more probable than not burden of proof. A comparison of a jury instruction under the substantial factor approach and R3 illuminates the difference between the two approaches as to operative nomenclature:
(3) There may be more than one cause present to produce an injury, and more than one person legally responsible for an injury. The plaintiff does not have to prove that the defendant’s negligence was the only or even the predominant cause of the injury. If two or more causes operating together contributed to the plaintiff’s injury so that, in effect, the damages suffered were inseparable, then it is enough for the plaintiff to prove that the defendant’s negligence was a substantial contributing factor in causing the injury. By “substantial” I mean that the defendant’s contribution to the harmful result, i.e., the defendant’s negligence, was not an insignificant factor.
The defendant’s negligence must contribute along with other factors to the result; it must be a material and important ingredient in causing the harm. If the defendant’s negligence was a substantial factor, then it is considered a cause of the plaintiff’s injury, and the plaintiff is entitled to recover. If it was not a substantial factor, if the negligence was only slight or tangential to causing the harm, then even though you may have found the defendant negligent, [it/he/she] cannot be held liable to pay damages to the plaintiff on this claim.