Three unknown assailants beat and attempted to rape Marianne Saelzler (plaintiff) one afternoon while she was trying to deliver a FedEx package at a 28-building apartment complex owned by Advanced Group 400 (defendant). A propped-open security gate could have allowed access, but Saelzler could not identify whether her assailants were trespassers or residents. The property owners knew about recurring criminal activity in the area, including juvenile-gang activity, because a gang evidently located its headquarters in one of the buildings. Multiple crimes involving tenants had been reported, and the security manager acknowledged several assaults and actual or attempted rapes occurred on the property during the preceding year. Management inspected the security gates regularly and provided nighttime security patrols, but not daytime patrols. Saelzler brought a negligence action asserting that Advanced Group 400 knew dangerous persons frequented the premises but failed to provide adequate security or warnings to others. Saelzler’s security expert testified that additional security measures would have prevented the attack. The trial court granted summary judgment for Advanced Group 400 based on lack of proximate cause. The appellate court reversed, reasoning that Saelzler made a sufficient showing, based on a complete lack of required security measures, to shift the burden of proof to the owner for purposes of summary judgment. Advanced Group 400 appealed to the California Supreme Court.