107 Cal.Rptr.2d 617 (2001) 25 Cal.4th 763 23 P.3d 1143

Marianne SAELZLER, Plaintiff and Appellant,
v.
ADVANCED GROUP 400 et al., Defendants and Respondents.

No. S085736.

Supreme Court of California.

May 31, 2001.

*618 Law Offices of Theodore Wolfberg, Daniel B. Wolfberg, Santa Monica, Andrew D. Wolfberg; Law Offices of Michael Paul Thomas and Michael Paul Thomas, Newport Beach, for Plaintiff and Appellant.

Early, Maslach, Price & Baukol and Priscilla F. Slocum, Los Angeles, for Defendants and Respondents.

Greines, Martin, Stein & Richland, Barbara W. Ravitz and Barbara Springer Perry, Beverly Hills, for Building Owners and Managers Association of Greater Los Angeles as Amicus Curiae on behalf of Defendants and Respondents.

Stephan, Oringher, Richman & Theodora, Harry W.R. Chamberlain II, Efrat M. Cogan; Robie & Matthai and Pamela E. Dunn, Los Angeles, for Association of Southern California Defense Counsel as Amicus Curiae on behalf of Defendants and Respondents.

Gordon & Rees, Michael T. Lucey and David Collins, San Francisco, for Association of Defense Counsel of Northern California and Nevada as Amicus Curiae on behalf of Defendants and Respondents.

Fred J. Hiestand, Sacramento, for the Civil Justice Association of California as Amicus Curiae on behalf of Defendants and Respondents.

Horvitz & Levy, Frederic D. Cohen, Andrea M. Gauthier, Encino, and Orly Degani, San Francisco, for the University of Southern California, the University of California, California State University, the Board of Trustees of the Leland Stanford Junior University, California Institute of Technology, Loma Linda University, Pepperdine University, Sutter Health, State Farm General Insurance Company, Truck Insurance Exchange, Fire Insurance Exchange, Mid-Century Insurance Company, Civic Property and Casualty Company, Exact Property and Casualty Company and Neighborhood Spirit Property and Casualty Company as Amici Curiae on behalf of Defendants and Respondents.

CHIN, J.

We granted review in this case to consider important issues concerning the liability of apartment owners and other business enterprises to persons injured on their premises by the criminal acts of others, a liability based solely on the business owners' negligent failure to provide adequate security measures to protect those who enter their property. The difficulty in resolving these issues is enhanced by the need to balance two important and competing policy concerns: society's interest in compensating persons injured by another's negligent acts, and its reluctance to impose unrealistic financial burdens on property owners conducting legitimate business enterprises on their premises.

*619 In this case, we attempt to balance these interests consistent with prior case precedent. As will appear, we conclude (contrary to the Court of Appeal below) that the trial court properly granted summary judgment to defendants based on plaintiffs failure adequately to demonstrate that defendants' negligence was an actual, legal cause of her injuries. Here, plaintiff alleged she was assaulted on defendants' premises by unknown assailants after she attempted to deliver a package to an apartment resident. Although plaintiffs evidence raised triable issues as to whether defendants owed her a duty of care and breached that duty by failing to provide additional security guards or functioning, locked security gates, her evidence was insufficient to show, as a triable factual issue, that defendants' asserted breach of duty actually caused her injuries. Plaintiff acknowledges that her assailants were never apprehended and their identity remains unknown to her. Accordingly, she is unable to prove they would not have succeeded in assaulting her if defendants had provided additional security precautions.

STANDARD OF REVIEW

Because plaintiff appeals from an order granting defendants summary judgment, we must independently examine the record to determine whether triable issues of material fact exist. (Code Civ. Proc., § 437c, subd. (c); see Guz v. Bechtel National, Inc. (2000) 24 Cal.4th 317, 334, 100 Cal. Rptr.2d 352, 8 P.3d 1089 (Guz); Sharon P. v. Arman, Ltd. (1999) 21 Cal.4th 1181, 1188, 91 Cal.Rptr.2d 35, 989 P.2d 121 (Sharon P.); Ann M. v. Pacific Plaza Shopping Center (1993) 6 Cal.4th 666, 673-674, 25 Cal.Rptr.2d 137, 863 P.2d 207 (Ann M.).) We stated in Sharon P., involving a similar negligence claim resolved on summary judgment, that "To prevail on her action in negligence, plaintiff must show that defendants owed her a legal duty, that they breached the duty, and that the breach was a proximate or legal cause of her injuries. (Ann M., supra, 6 Cal.4th at p. 673, 25 Cal.Rptr.2d 137, 863 P.2d 207.) Since defendants obtained summary judgment in their favor, `we review the record de novo to determine whether [they have] conclusively negated a necessary element of the plaintiffs case or demonstrated that under no hypothesis is there a material issue of fact that requires the process of trial.' (Id. at pp. 673-674, 25 Cal.Rptr.2d 137, 863 P.2d 207.)" (Sharon P., supra, 21 Cal.4th at p. 1188, 91 Cal.Rptr.2d 35, 989 P.2d 121.)

We recently observed in Guz that amendments to the California summary judgment statute may have modified the foregoing traditional rule by clarifying that "a moving defendant could obtain summary judgment solely by showing after opportunity for discovery, that the opposing plaintiff had failed to present triable evidence crucial to his case [citation]." (Guz, supra, 24 Cal.4th at p. 335, fn. 7, 100 Cal.Rptr.2d 352, 8 P.3d 1089; see also id. at pp. 372-374, 100 Cal.Rptr.2d 352, 8 P.3d 1089 (cone. opn. of Chin, J.); Code Civ. Proc., § 437c, subd. (o)(2) [if defendant shows element of plaintiffs case cannot be established, burden shifts to plaintiff to show triable issue of fact, a showing supported by "specific facts," not mere "allegations or denials of its pleadings"]; Leslie G. v. Perry & Associates (1996) 43 Cal. App.4th 472, 482, 50 Cal.Rptr.2d 785 (Leslie G.).)

We agree that the amendments to Code of Civil Procedure section 437c have modified the rule recited in Sharon P. As stated in Scheiding v. Dinwiddie Construction Co. (1999) 69 Cal.App.4th 64, 70, 81 Cal.Rptr.2d 360 (Scheiding), "We begin by observing that the nature of summary *620 judgment in California has changed dramatically over the last 10 years. The shifting of the burden of producing evidence that lies at the heart of this appeal could not have occurred under the summary judgment law as it previously existed. Formerly, a moving defendant had to affirmatively negate a cause of action and could not attempt to rely on a plaintiffs vague or otherwise insufficient responses to discovery. Prior to the amendments of section 437c, the burden of proof rested entirely on the moving party to establish a right to summary judgment by demonstrating the negative proposition that the opposing party could not prevail. [Citations.] In most cases, this was a burden impossible to bear." (Italics added.)

Scheiding continued, pointing out that "The 1992 and 1993 amendments ... did not change the fundamental requirement that the moving party prove its right to summary judgment, but did adopt the federal mechanism of burden shifting. The new statute expressly provided that the burden does not shift to a responding party until the moving party (in this context, as usual, a defendant or cross-defendant) has been able to `show' that a cause of action has no merit `because an element of the claim cannot be established or there is a complete defense.' Thus, the amended language of [Code of Civil Procedure] section 437c, like its counterpart Federal Rules of Civil Procedure, rule 56 (28 U.S.C.), now places the initial burden on the moving party, and shifts it to the opposing party upon a `showing' that one or more elements of the cause of action cannot be established. [Citation.]" (Scheiding, supra, 69 Cal.App.4th at pp. 71-72, 81 Cal.Rptr.2d 360, italics added; see also Union Bank v. Superior Court (1995) 31 Cal.App.4th 573, 581-592, 37 Cal.Rptr.2d 653 [legislative history of 1992 and 1993 amendments].)

Therefore, we must determine whether defendants in the present case have shown, through the evidence adduced in this case, including security records and deposition testimony, that plaintiff Saelzler has not established, and cannot reasonably expect to establish, a prima facie case of causation, a showing that would forecast the inevitability of a nonsuit in defendants' favor. If so, then under such circumstances the trial court was well justified in awarding summary judgment to avoid a useless trial. (See Guz, supra, 24 Cal.4th at p. 374, 100 Cal.Rptr.2d 352, 8 P.3d 1089 (cone. opn. of Chin, J.).)

In performing our de novo review, we must view the evidence in a light favorable to plaintiff as the losing party (Molko v. Holy Spirit Assn. (1988) 46 Cal.3d 1092, 1107, 252 Cal.Rptr. 122, 762 P.2d 46), liberally construing her evidentiary submission while strictly scrutinizing defendants' own showing, and resolving any evidentiary doubts or ambiguities in plaintiffs favor. (Marshak v. Ballesteros (1999) 72 Cal.App.4th 1514, 1517, 86 Cal.Rptr.2d 1; Kaplan v. LaBarbera (1997) 58 Cal. App.4th 175, 179, 67 Cal.Rptr.2d 903.) We have concluded that, even giving plaintiff the benefit of these favorable rules of construction, her submission in opposition to summary judgment lacked specific facts showing that defendants' alleged negligence was an actual, legal cause of her injuries. In other words, defendants have shown that plaintiff has not established, and cannot reasonably expect to establish, a prima facie case of causation.

FACTS

On March 15, 1996, plaintiff Marianne Saelzler was an employee of Federal Express. Defendants were owners of the Sherwood Apartments, a 28-building, 300-unit apartment complex located on a several-acre site in Bellflower. Plaintiff came *621 to the complex in midafternoon to deliver a package to a resident. As she entered through one of the many gated entrances to the premises, she saw two young men loitering outside a security gate that had been propped open. While walking across the grounds she saw another young man already on the premises.

Plaintiffs attempt to deliver the package proved unsuccessful because the resident was not at home. When plaintiff returned down a walk path with the package in hand, the three men confronted her, and one of them asked, "Where do you think you're going?" When she failed to reply, another one said, "You're not going anywhere." Then the three of them beat her and attempted to rape her, inflicting serious injuries. After assaulting plaintiff, her assailants fled and were never apprehended.

Plaintiffs complaint alleged that defendants, knowing that dangerous persons frequented their premises, nonetheless failed to maintain the premises in a safe condition, failed to provide adequate security, and failed to warn others of the unsafe conditions. Defendants moved for summary judgment on the basis that plaintiff was unable to establish any substantial causal link between defendants' omissions and plaintiffs injury. Plaintiff offered no evidence showing the identity of her assailants, whether they were gang members, whether they trespassed on defendants' property to assault her, or whether they were tenants of the building who were permitted to pass through the security gates. Similarly, plaintiff submitted no evidence showing that the propped-open security gate was actually broken or otherwise not functioning properly, or whether her assailants entered through the gate or themselves broke it and entered. Finally, plaintiff offered no evidence that defendants reasonably or effectively could have warned members of the public such as plaintiff of unspecified dangers from unknown assailants frequenting the area.

As the trial court found, plaintiff presented evidence that defendants knew of frequent recurring criminal activity on the premises of their 28 building apartment complex. The community of Bellflower was itself a high-crime area, with considerable juvenile gang activity occurring both on and off defendants' premises. Plaintiff provided police reports and security logs showing that within the year prior to her assault, defendants received 41 reports of trespass, and 45 reports of occasions in which various perimeter fences and gate doors were broken or rendered inoperable. The list of criminal activity on the premises included incidents of gunshots, robberies, and sexual harassment of women, including sexual assaults and rapes.

Defendants' security manager acknowledged that during the year preceding the assault on plaintiff, several nighttime assaults, and actual or attempted rapes, occurred on the premises. Plaintiff produced evidence that a gang called the 706 Hustlers was reportedly "headquartered" in one of defendants' apartment buildings, conducting drug transactions, and hitting and intimidating other people on the premises. In the year prior to the incident involving plaintiff, sheriffs officers came to the Sherwood Apartments approximately 50 times. Much of this criminal activity was reported to defendants' manager, either in daily incident reports from their nighttime security officers or in police reports. Some pizza parlors refused to deliver to apartments in the complex, insisting residents come to the sidewalk if they wanted delivery of pizzas ordered by phone. Defendants' apartment manager used security personnel to escort her to her vehicle whenever she left the premises.

*622 On the other hand, defendants' security logs showed that they took some steps to control the situation, hiring security guards to patrol the premises at night, and making frequent and regular attempts to repair broken locks or nonfunctioning gates. The record indicates that these guards were on daily duty from approximately 5:00 p.m. to 5:00 a.m. Defendants' manager stated that the guards' starting times ranged from 3:00 p.m. to 5:00 p.m., to make their schedule less predictable, and that defendants occasionally, on a random basis, employed full-time 24 hour security patrols on the premises. Defendants imposed a nighttime curfew on juveniles, and posted notices threatening eviction of tenants involved with drugs or gang activities. Defendants' security logs indicated their manager and security guards regularly checked access gates for forced entry and broken locks, broke up fights, forced aggressive tenants or trespassers to leave the area, and evicted tenants involved in criminal or gang activity.

Plaintiff observes that police officers advised both defendants' apartment manager and the head of the security firm they employed that they should hire daytime as well as nighttime security patrols. Plaintiff filed a lengthy declaration from a security expert, Robert Feliciano, who had reviewed the security logs and depositions and had personally visited the Sherwood Apartments complex. His qualifications included service as Director of Police and Safety for the Housing Authority of Los Angeles County, as well as advanced education in public safety and several years in law enforcement. At the time he made his declaration, he was a full-time instructor in criminal justice and police science at a community college. Feliciano expressed the opinion "that this attack, assault and battery, and attempted rape on the plaintiff would not have occurred had there been daytime security and a more concerted effort to keep the gates repaired and closed.... It is my opinion that the premises were a haven for gangsters and hoodlums which further encouraged criminal activity as evidence [sic ] by the long history of criminal activity in the only one year prior to this incident."

The trial court granted summary judgment for defendants, finding plaintiff had failed to show defendants' breach of duty to safeguard her was a proximate cause of her assault. Based on the parties' submissions, the court found "overwhelming evidence" of prior incidents of trespass and broken or inoperable perimeter fences or gates, and a "long list" of criminal activity on the premises, including a juvenile gang possibly "headquartered" there. But despite establishing the "high foreseeability" that violent crime would occur on the premises, and defendants' resultant duty to provide increased security, the court found that plaintiff failed to establish a "reasonably probable causal connection" between defendants' breach of duty and plaintiffs injuries.

A majority of the Court of Appeal reversed, concluding that plaintiffs showing was sufficient to raise a triable causation issue for the jury. In summary, the majority held, relying primarily on commonsense and ordinary experience, that defendants' "complete absence of required security measures" by itself reasonably could be deemed a contributing cause of any criminal activity in the area.

The Court of Appeal majority also held that defendants' failure to provide additional security justified shifting the burden of proof to defendants, for purposes of their summary judgment motion, to conclusively establish the absence of a causal relation between their breach of duty and the assault on plaintiff by showing this particular assault would have occurred *623 even if reasonable security measures had been taken. Because defendants "created this situation" by their flagrant failure to provide any additional daytime security, plaintiff should be relieved of her responsibility to prove a causal link between defendants' breach of duty and the assault which produced her injuries.

Finally, according to the Court of Appeal majority, the testimony of plaintiffs expert, opining that the assault on plaintiff would not have occurred but for the lack of daytime security measures, was "both admissible and credible" on the causation issue.

The Court of Appeal dissent reasoned that although security measures such as guards, lights, or gates may lessen the general probability of crime occurring on the premises, plaintiff presented no evidence that such measures would have succeeded in thwarting her assailants. The dissent observed that "Neither appellant nor anyone else knows who the attackers were; they may have lived in the complex and possessed keys to the gate. Even if the attackers were nonresidents, a functioning gate would not necessarily have kept them out. The attackers might have followed [plaintiff] or some other tenant in while the gate was open, or climbed over the gate. The complex had numerous auto and pedestrian entrances through which the attackers might have come.

"Likewise, it cannot be known whether more security guards would have prevented the attack. A 300-unit, 28-building apartment complex contains many rooms, halls, entries, garages and other spaces where a rape could take place despite extensive security patrols. Again, though one can generalize that increased security patrols probably would have lessened the incidence of crime in the complex, we can never know whether they would have prevented the attack on appellant. The security officer's logs in evidence did show that there were regular security patrols on the premises, and despite these, the attack on [plaintiff], and other crimes as well, occurred."

DISCUSSION

As indicated, in this case plaintiff, injured on defendants' premises by the criminal assault of unknown assailants, seeks to recover damages from defendants on the theory that they breached their duty of care toward her. In a recent case, we explained that to prevail in such a case, the plaintiff must show that the defendant owed her a legal duty of care, the defendant breached that duty, and the breach was a proximate or legal cause of her injury. (Sharon P., supra, 21 Cal.4th at p. 1188, 91 Cal.Rptr.2d 35, 989 P.2d 121; accord, Ann M., supra, 6 Cal.4th at p. 673, 25 Cal.Rptr.2d 137, 863 P.2d 207; see Rest.2d Torts, § 281.) Although plaintiff devotes a substantial portion of her brief to the issue of defendants' duty of care, defendants do not contest, for purposes of their summary judgment motion, that they may have owed and breached a duty of care toward plaintiff. Here, we are solely concerned with the issue of causation. Was defendants' possible breach of duty a substantial factor in causing plaintiffs injuries?

In Sharon P., the plaintiff was criminally assaulted by unknown assailants in an underground parking garage. She sued the garage owner for failure to provide adequate security measures for its tenants and, as here, the trial court granted summary judgment against her. Although in Sharon P. we were concerned with the question of the defendants' duty to provide security guards and other security measures, we also spoke briefly on the separate subject of causation, observing that it was "questionable whether plaintiffs proposed *624 [security] measures would have been effective to protect against the type of violent assault that occurred here." (Sharon P., supra, 21 Cal.4th at p. 1196, 91 Cal.Rptr.2d 35, 989 P.2d 121.) We noted that the courts "have rejected claims of abstract negligence pertaining to the lighting and maintenance of property where no connection to the alleged injuries was shown. [Citations.]" (Id. at pp. 1196-1197, 91 Cal.Rptr.2d 35, 989 P.2d 121, fn. omitted, italics added.)

In Sharon P., supra, 21 Cal.4th at page 1197, 91 Cal.Rptr.2d 35, 989 P.2d 121, we cited with approval three Court of Appeal cases holding that, assuming the defendant owed and breached a duty of care to the plaintiff, she nonetheless cannot prevail unless she shows the breach bore a causal connection to her injury. (Nola M. v. University of Southern California (1993) 16 Cal.App.4th 421, 435-439, 20 Cal. Rptr.2d 97 (Nola M.); Constance B. v. State of California (1986) 178 Cal.App.3d 200, 211-212, 223 Cal.Rptr. 645 (Constance B.); Noble v. Los Angeles Dodgers, Inc. (1985) 168 Cal.App.3d 912, 915-918, 214 Cal.Rptr. 395 (Noble).) These cases are close on point and their analyses are instructive.

In Noble, the plaintiff was assaulted in a parking lot at Dodger Stadium and sued the stadium owner on the theory it failed to provide adequate security for its patrons. At trial, the plaintiffs expert witness opined that the owner should have employed more security guards to patrol the area, and the jury awarded the plaintiff substantial damages. On appeal, the court reversed, holding that "abstract negligence," without proof of a causal connection between the defendant's breach and the plaintiffs injury, is insufficient to sustain the award. (Noble, supra, 168 Cal. App.3d at pp. 916, 918, 214 Cal.Rptr. 395.)

In Constance B., the plaintiff was assaulted at night in the restroom at a state highway rest area. The appellate court affirmed a grant of summary judgment in defendant state's favor, holding that the plaintiff, who saw her attacker watching her when she entered the restroom, failed to submit evidence showing that additional lighting would have prevented the attack. (Constance B., supra, 178 Cal.App.3d at pp. 211-212, 223 Cal.Rptr. 645.) The court observed that "If liability may be premised solely on this notion [that criminals are generally deterred by strong lighting], proprietors will become the insurers of the safety of persons on their premises, subject only to the caprice of particular juries. [Citation.]" (Id. at p. 212, 223 Cal.Rptr. 645.)

In Nola M., the plaintiff was raped on a college campus and sued the college on the theory it should have provided more campus security. On appeal from a judgment in the plaintiffs favor, the Nola M. court reversed. The court assumed for purposes of argument that the plaintiff had submitted sufficient evidence that the defendant breached a duty of care toward her, but concluded that she failed to prove the breach was a legal cause of the assault. (Nola M., supra, 16 Cal.App.4th at pp. 427-428, 20 Cal.Rptr.2d 97.) The court observed that to demonstrate actual or legal causation, the plaintiff must show that the defendant's act or omission was a "substantial factor" in bringing about the injury. (Id, at p. 427, 20 Cal.Rptr.2d 97; see Mitchell v. Gonzales (1991) 54 Cal.3d 1041, 1049, 1052-1054, 1 Cal.Rptr.2d 913, 819 P.2d 872; Rest.2d Torts, §§ 430, 431, subd. (a).) Nola M. concluded that the plaintiff must do more than simply criticize, through the speculative testimony of supposed security "experts," the extent and worth of the defendant's security measures, and instead must show the injury was actually caused by the failure to provide *625 greater measures. (Nola M., supra, 16 Cal.App.4th at p. 435, 20 Cal.Rptr.2d 97.) The court observed that a different rule would "make the landowner the insurer of the absolute safety of everyone who enters the premises." (Id. at p. 437, 20 Cal.Rptr.2d 97.)

In addition to the foregoing three appellate cases cited in our Sharon P. decision, other California cases support the rule that the plaintiff must establish, by nonspeculative evidence, some actual causal link between the plaintiffs injury and the defendant's failure to provide adequate security measures. (See Leslie G, supra, 43 Cal.App.4th at pp. 480-488, 50 Cal.Rptr.2d 785; Thai v. Stang (1989) 214 Cal.App.3d 1264, 1276, 263 Cal.Rptr. 202 [characterizing as "pure speculation" expert testimony that absence of added security contributed to criminal assault]; Lopez v. McDonald's Corp. (1987) 193 Cal.App.3d 495, 515, 238 Cal.Rptr. 436 [restaurant's failure to hire security guard not shown to have been "substantial factor" in causing injuries from gunman's attack].)

Although each of the foregoing cases supports defendants' position here, Leslie G. is perhaps closest on point, being an appeal following summary judgment for the defendant. There, the plaintiff alleged she was raped by an unknown assailant while in the garage of her apartment building. She sued the building owners, asserting their negligence in failing to repair a broken security gate might have allowed her assailant to enter the garage. As in the present case, the plaintiffs security expert testified at his deposition that the apartment was located in a high-crime area, that functioning security gates were critical to ensuring tenants' safety, and that the nonfunctioning gates allowed the assailant to enter and ultimately assault the plaintiff. The expert stated his opinion that the defendant should have hired an on-site manager to perform regular inspections and repairs of the gate and other entrances, to ensure the building's continued safety. He also opined that the assailant had selected the garage because of its isolated, remote nature, and the opportunities to hide and escape if necessary. (Leslie G., supra, 43 Cal.App.4th at pp. 478-479, 50 Cal.Rptr.2d 785.)

In Leslie G, as here, the trial court granted the defendant summary judgment on the ground the plaintiff had failed to establish a sufficient causal connection between the defendant's negligence and the assault. Unlike the present case, in Leslie G. the Court of Appeal affirmed summary judgment, holding that the security expert's opinions were too speculative to furnish a causal link between the defendant's negligence and the assault. The court also observed that "Since there is no direct evidence that the rapist entered or departed through the broken gate (or even that the broken gate was the only way he could have entered or departed), [plaintiff] cannot survive summary judgment simply because it is possible that he might have entered through the broken gate. [Citations.]" (Leslie G., supra, 43 Cal.App.4th at p. 483, 50 Cal.Rptr.2d 785.)

As here, the plaintiff in Leslie G. had argued that her expert's opinion testimony was sufficient to create a triable issue of fact regarding causation. The court disagreed, observing that expert opinion resting solely on speculation and surmise is inadequate to survive summary judgment because it fails to establish a "`reasonably probable causal connection'" between the defendant's negligence and the plaintiffs injury. (Leslie G, supra, 43 Cal.App.4th at p. 487, 50 Cal.Rptr.2d 785, quoting from an earlier case; italics omitted.) The court concluded that "a tenant's negligence action against her landlord for injuries resulting from the criminal assault of a third *626 person must be supported by evidence establishing that it was more probable than not that, but for the landlord's negligence, the assault would not have occurred. Where, as here, there is evidence that the assault could have occurred even in the absence of the landlord's negligence, proof of causation cannot be based on mere speculation, conjecture and inferences drawn from other inferences to reach a conclusion unsupported by any real evidence, or on an expert's opinion based on inferences, speculation and conjecture. [¶] In this case, where there is no factual basis for the expert's opinion or for [the plaintiffs] general assertion of causation, the conclusion is unavoidable that summary judgment was properly granted." (Id. at p. 488, 117 Cal.Rptr. 749, italics added, fn. omitted.)

Leslie G. and the other cases cited above fully support the trial court's summary judgment ruling in this case. Here, by reason of the prior criminal assaults and incidents on the premises, defendants may have owed a duty to provide a reasonable degree of security to persons entering them. For purposes of discussion, we assume defendants breached that duty by failing (1) to keep all entrance gates locked and functioning, and (2) to provide additional daytime security guards to protect persons such as plaintiff. But the evidence fails to show that either breach contributed to plaintiffs injuries in this case. As Professors Prosser and Keeton observe, "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." (Prosser & Keeton, Torts (5th ed.1984) § 41, p. 269, fns. omitted, italics added.)

Plaintiff admits she cannot prove the identity or background of her assailants. They might have been unauthorized trespassers, but they also could have been tenants of defendants' apartment complex, who were authorized and empowered to enter the locked security gates and remain on the premises. The primary reason for having functioning security gates and guards stationed at every entrance would be to exclude unauthorized persons and trespassers from entering. But plaintiff has not shown that her assailants were indeed unauthorized to enter. Given the substantial number of incidents and disturbances involving defendants' own tenants, and defendants' manager's statement that a juvenile gang was "headquartered" in one of the buildings, the assault on plaintiff could well have been made by tenants having authority to enter and remain on the premises. That being so, and despite the speculative opinion of plaintiffs expert, she cannot show that defendants' failure to provide increased daytime security at each entrance gate or functioning locked gates was a substantial factor in causing her injuries. (See Nola M., supra, 16 Cal. App.4th at p. 427, 20 Cal.Rptr.2d 97; Mitchell v. Gonzales, supra, 54 Cal.3d at pp. 1049, 1052-1054, 1 Cal.Rptr.2d 913,