What is the test for determining whether a plaintiff is a sole or superseding cause in a motor vehicle accident?

"[I]t is only an unforeseeable intervening cause, an extraordinary and abnormal occurrence, which rises to the level of an exonerating, superseding cause. [Citations.]" (People v. Armitage, supra, 194 Cal.App.3d at pp. 420-421.) "Facts attacking legal causation are only relevant if the defendant's act was not a substantial factor in producing the harm or injurious situation. [Citation.]" (People v. Wattier (1996) 51 Cal.App.4th 948, 953, italics in original.) To constitute a sole or superseding cause, the victim's conduct must have been "so unusual, abnormal, or extraordinary that it could not have been foreseen. [Citation.]" (People v. Schmies, supra, 44 Cal.App.4th at p. 52, italics added.) Absent such conduct, evidence the victim "may have shared responsibility or fault for the accident does nothing to exonerate [a] defendant for his role" and "is not relevant." (Id. at p. 51.)

"[A] superseding cause must break the chain of causation after the defendant's act before he or she is relieved of criminal liability for the resulting harm." (People v. Wattier, supra, 51 Cal.App.4th at p. 953, italics in original.)

Page 32