What is the burden of proving negligence against a store owner?

A store owner is not the insurer of its patrons' personal safety, but does owe patrons a duty to exercise reasonable care in keeping the premises reasonably safe. (See Ortega v. Kmart Corp., supra, 26 Cal.4th at p. 1205.) To establish the owner's liability on a negligence theory, the plaintiff must prove duty, breach, causation and damages. (Ibid.) "A plaintiff meets the causation element by showing that (1) the defendant's breach of its duty to exercise ordinary care was a substantial factor in bringing about plaintiff's harm, and (2) there is no rule of law relieving the defendant of liability. [Citation.] These are factual questions for the jury to decide, except in cases in which the facts as to causation are undisputed." (Ibid.) To meet its burden of proof, a "'plaintiff must introduce evidence which affords a reasonable basis for the conclusion that it is more likely than not that the conduct of the defendant was a cause in fact of the result. A mere possibility of such causation is not enough; and when the matter remains one of pure speculation or conjecture, or the probabilities are at best evenly balanced, it becomes the duty of the court to direct a verdict for the defendant.' [Citation.]" (Id. at pp. 1205-1206.)