In Arizona, negligence can be presumed if you are injured while someone is breaking the law. What does that mean for your personal injury claim?

There are a few caveats. The law must have been enacted “for the protection and safety of the public.” Second, the law must “express rules of conduct in specific and concrete terms as opposed to general or abstract principles.” Good v. City of Glendale, 150 Ariz. 218, 221 (Ct. App. 1986). Furthermore, the victim must be the type of person that the law was intended to protect. Therefore, if a person crashes into a cyclist while speeding, the cyclist, as member of the class of protected persons, can use negligence per se in his case against the speeder. If a car passing by in the opposite lane is distracted by the crash scene and rear-ends the car in front of her, she will not be considered a member of the class of people the speeding law was meant to protect and will be unable to use negligence per se in her potential claim against the speeder.

What does this mean for the average personal injury case? In order to win a personal injury case, the victim/plaintiff, must prove 1) that the defendant was negligent, 2) that the plaintiff was injured, and 3) that the defendant’s negligence was a cause of the plaintiff’s injury. A person can be negligent without breaking any laws. However, if a jury believes that the defendant broke a law, then the jury must find that person to also be negligent. Therefore, one of the three pillars of proving negligence is no longer at issue. If a jury decides that a defendant ran a red light, then that defendant must be considered negligent. If a jury decides that a defendant was speeding at the time of the crash, then the jury must also find the defendant to be negligent.

The two remaining pillars of negligence must still be proven. That is, the plaintiff must convince a jury that there 1) was an injury that, 2) was caused by the negligence/law violation. The negligence per se doctrine’s presumption of negligence makes proving one’s case easier.

Here is an example where negligence per se may play a substantial role in a trial:

Plaintiff claims that Defendant ran a red light and crashed into her car, causing her to break her ankle and injure her back. Defendant claims that he had a yellow light and that Plaintiff should not have been in the intersection. A jury, after hearing the facts, determines that Defendant did indeed run a red light. Therefore, the jury must, by the doctrine of negligence per se, find the defendant to be negligent. The jury is then tasked with deciding whether the Defendant’s negligence was in fact the cause of the Plaintiff’s injury.

While it may seem like common sense, the doctrine of negligence per se plays a vital role in nearly all personal injury claims, even those that never make it to trial.