What is the test for establishing a causation element in a negligence claim?

To meet the causation element in a negligence theory, a plaintiff must show that the defendant's negligence "was a substantial factor in bringing about plaintiff's harm" and that "there is no rule of law relieving the defendant of liability." (Ortega v. Kmart Corp. (2001) 26 Cal.4th 1200, 1205.) The plaintiff generally has the burden of proof in establishing the causation element in a negligence theory; the plaintiff must present evidence showing it is more likely than not that the defendant's conduct was a cause-in-fact. (Ibid.)