The majority upholds the trial court’s grant of summary judgment to defendants, at whose apartment complex plaintiff, a Federal Express employee who was trying to deliver a package, suffered a brutal sexual assault by three men who were never apprehended. Only by bending both the rules of summary judgment and the legal causation element of negligence can the majority reach its result. The holding places a virtually insurmountable barrier in the path of any plaintiff seeking to recover damages for injuries allegedly suffered as a result of a property owner’s unreasonable failure to provide security to protect against foreseeable third party criminal acts. I cannot and do not join in that holding.
I
After the sexual attack described above, plaintiff sued defendants, seeking • damages for personal injury. She alleged that defendants knew of dangerous persons frequenting their property, yet failed to maintain the premises in a safe condition, failed to provide adequate security, and failed to warn of unsafe conditions.
Defendants moved for summary judgment, asserting that plaintiff could not show that they had caused her injuries. In opposition, plaintiff presented the following evidence; Pizza parlors refused to deliver to the apartment *782complex. Defendants’ own apartment manager relied on security personnel to escort her to her car whenever she left the property. During the year before the attack on plaintiff, security personnel reported to the building’s management 45 instances of broken fences or gates and 41 trespass incidents, and police responded to the complex some 50 times. Criminal activities on the property included gunfire, robberies, rapes, and other sexual assaults. The premises were the headquarters for the 706 Hustlers, a gang that conducted drug transactions and assaulted and threatened others on the property. Although security guards patrolled the complex at night, defendants provided none during the day even though the police had suggested that they do so.
After reviewing defendants’ security logs and depositions and visiting the complex, plaintiff’s security expert concluded that the attack would have been prevented had defendants provided daytime security at the complex.
The trial court found “overwhelming evidence” of recurring criminal activities on defendants’ property, making it highly foreseeable that violent crime would occur on the property. The court nevertheless felt compelled to grant defendants’ motion: “The Court notes that the facts of this case are particularly troubling and may warrant the Court of Appeal reviewing the status of the law as it relates to the Nola M. [v. University of Southern California (1993) 16 Cal.App.4th 421 [20 Cal.Rptr.2d 97]] and Leslie G. [v. Perry & Associates (1996) 43 Cal.App.4th 472 [50 Cal.Rptr.2d 785]] cases which seem to compel the ruling set forth above.” Both cases hold that a plaintiff seeking to establish that a property owner’s failure to provide security is the cause of a criminal assault by a third party must show the security would have prevented the assault. (Nola M. v. University of Southern California, supra, at pp. 436-437 & fn. 10; Leslie G. v. Perry & Associates, supra, at p. 488.)
The Court of Appeal in a split decision reversed the summary judgment in favor of defendants. We granted defendants’ petition for review. Today, a majority of this court in turn reverses the Court of Appeal’s judgment.
II
The majority concludes that plaintiff cannot show a causal connection between her injuries and defendants’ breach of the duty of reasonable care they owed plaintiff unless she establishes that her assailants “would not have succeeded in assaulting her if defendants had provided additional security precautions” (maj. opn., ante, at p. 767) or, stated differently, “that roving guards would have encountered her assailants or prevented the attack” (id. at *783p. 777). In essence, the majority imposes on plaintiff the burden of showing causation with certainty. This is wrong.
Even at trial, a plaintiff need not establish causation with certainty. (Valdez v. J. D. Diffenbaugh Co. (1975) 51 Cal.App.3d 494, 509 [124 Cal.Rptr. 467]; Ahrentzen v. Westburg (1968) 263 Cal.App.2d 749, 751 [69 Cal.Rptr. 916].) As Dean Prosser explained more than half a century ago: “In the ordinary case the question becomes one of what would have happened if the defendant had acted otherwise. This is of course incapable of mathematical proof, and a certain element of guesswork is always involved. Proof of the relation of cause and effect can never be more than ‘the projection of our habit of expecting certain consequents to follow certain antecedents merely because we have observed those sequences on previous occasions.’ When a child is drowned in a swimming pool, no one can say with certainty that a lifeguard would have saved him; but the experience of the community is that with guards present people are commonly saved, and this affords a sufficient basis for the conclusion that it is more likely than not that the absence of the guard played a significant part in the drowning. Such questions are peculiarly for the jury. Whether proper construction of a building would have withstood an earthquake, whether reasonable police precautions would have prevented a boy from shooting the plaintiff in the eye with an airgun, whether a broken flange would have made an electric car leave the rails in the absence of excessive speed, whether a collision would have occurred if the defendant had not partially obstructed the highway, and many similar questions, cannot be decided as a matter of law.” (Prosser, Proximate Cause in California (1950) 38 Cal. L.Rev. 369, 382-383, fns. omitted, italics added.) This court quoted Dean Prosser’s statement with approval in Campbell v. General Motors Corp. (1982) 32 Cal.3d 112, 120 [184 Cal.Rptr. 891, 649 P.2d 224, 35 A.L.R.4th 1036].
Thus, under well-established law plaintiff here need not prove with certainty that the presence of security guards would have prevented the sexual assault.
Ill
After imposing on plaintiff the burden of showing causation with certainty, the majority also concludes that defendants are entitled to summary judgment unless plaintiff proves “it was ‘more probable than not’ that additional security precautions would have prevented the attack.” (Maj. opn., ante, at p. 776.) Again, the majority is wrong.
At the summary judgment stage, the plaintiff need only produce evidence sufficient to permit a reasonable trier of fact to infer that it is more probable *784than not that the defendants caused the injury. A motion for summary judgment may be granted only when no “triable issue of one or more material facts” remains for trial. (Code Civ. Proc., § 437c, subd. (o)(l) & (2), italics added.) A triable issue of material fact exists when the evidence as a whole is sufficient to permit a reasonable trier of fact to infer the existence of the requisite fact. (Code Civ. Proc., § 437c, subd. (c); CalvilloSilva v. Home Grocery (1998) 19 Cal.4th 714, 735-736 [80 Cal.Rptr.2d 506, 968 P.2d 65].) Thus, the critical inquiry at the summary judgment stage is not whether the court ruling on a summary judgment motion, or an appellate court reviewing that ruling, concludes the plaintiff has produced evidence that an element of the plaintiff’s cause of action is more probable than not. Rather, it is whether the plaintiff has produced evidence from which a reasonable trier of fact could conclude that the evidence is sufficient to establish that an element of the cause of action is more probable than not.
This distinction is critical. Surely some reasonable jurors could conclude that it is more probable than not that the presence of security guards would have deterred the attack on plaintiff here. Although there may be some criminals so reckless as to attack a person in broad daylight notwithstanding the presence of security guards, common sense suggests that such criminals are a minority. Knowing nothing about plaintiff’s never-apprehended assailants, a jury might reasonably conclude that such individuals are more likely to be among the typical class of criminals who would be deterred by the presence of security guards instead of among the reckless few who would not.
The majority’s errors deprive plaintiff of her constitutional right to a trial by jury. A judge ruling on a motion for summary judgment is not sitting as a trier of fact. When, as here, the plaintiff has a triable issue of material fact it is the jury that must decide the issue. (Reeves v. Sanderson Plumbing Products, Inc. (2000) 530 U.S. 133, 150 [120 S.Ct. 2097, 2110, 147 L.Ed.2d 105]; Rest.2d Torts, § 328C, subd. (a); Prosser & Keeton, Torts (5th ed. 1984) § 41, p. 267.)
IV
Here, plaintiff offered evidence from which a reasonable trier of fact could find that defendants’ failure to maintain their property in a safe condition was more than a minimal cause of plaintiff’s assault. (See dis. opn. of Werdegar, J., post, at pp. 792-794.) Plaintiff need show nothing more to avoid summary judgment.
I would affirm the judgment of the Court of Appeal.
Werdegar, J., concurred.