Twelve-year old Damechie Mitchell, the son of James and Joyce Mitchell (plaintiffs), was invited to a lake by his friend Luis and Luis’s parents, Jose and Matilde Gonzales (defendants). Joyce allegedly told Matilde that Damechie could not swim and should be kept ashore. Matilde denied the conversation. Without Jose or Matilde’s knowledge, Luis and Damechie took a paddleboard onto the lake. Damechie told Luis he could not swim and asked for help if he fell into the water. Luis began rocking the paddleboard and tipped it, causing both boys to fall off. When Damechie tried to grab onto Luis, Luis pushed him away. Damechie drowned. The Mitchells sued the Gonzaleses for negligence in a California state court. At trial, the parties requested different jury instructions on causation. The Gonzaleses requested Book of Approved Jury Instructions (BAJI) No. 3.75: “A proximate cause of [injury] . . . is a cause which, in natural and continuous sequence, produces the [injury] . . . and without which the [injury] . . . would not have occurred.” The Mitchells requested BAJI No. 3.76, which defined the cause of injury as “a cause which is a substantial factor in bringing about the [injury].” The trial court gave BAJI No. 3.75 as an instruction. In closing argument, counsel for the Gonzaleses emphasized Damechie’s knowing inability to swim. The jury found, by an overwhelming margin, that the defendants were negligent. They also concluded, however, by an overwhelming margin, that the defendants’ negligence did not cause Damechie’s death. The Mitchells appealed.