Negligence per se is a legal doctrine where a defendant is presumed to be liable for a plaintiff's damages if the defendant's violation of a statute caused the plaintiff's injuries. Think of it as "automatic" liability for a driver who causes a car accident because he or she is speeding. Of course you still need to establish the injuries and damages caused by the car accident, but you are well on your way.
"Negligence per se" is not available in every case. But if you can show that a defendant violated a statute - and that the statute was designed to prevent injuries just like yours - then you have negligence per se. The only thing a defendant can do is try to explain his or her way out of liability.
California's negligence per se doctrine is codified in California Evidence Code §669, which provides:
(a) The failure of a person to exercise due care is presumed if:
(1) He violated a statute, ordinance, or regulation of a public entity;
(2) The violation proximately caused death or injury to person or property;
(3) The death or injury resulted from an occurrence of the nature which the statute, ordinance, or regulation was designed to prevent; and
(4) The person suffering the death or the injury to his person or property was one of the class of persons for whose protection the statute, ordinance, or regulation was adopted.
(b) This presumption may be rebutted by proof that:
(1) The person violating the statute, ordinance, or regulation did what might reasonably be expected of a person of ordinary prudence, acting under similar circumstances, who desired to comply with the law; or
(2) The person violating the statute, ordinance, or regulation was a child and exercised the degree of care ordinarily exercised by persons of his maturity, intelligence, and capacity under similar circumstances, but the presumption may not be rebutted by such proof if the violation occurred in the course of an activity normally engaged in only by adults and requiring adult qualifications.
So if you are in a car accident - and the car accident was caused by the defendant speeding, you can ask the jury for a determination of negligence per se, or an "automatic" finding that the defendant was negligent.
Pete Clancy is an Oakland personal injury attorney.