Mesa AZ | Personal Injury attorney Brian T. Allen discusses Negligence Per Se in the following post:

Criminal prosecutions revolve around written law – law that is “on the books.” Local, state, and federal laws set the parameters of criminal conduct and the standards by which criminals are to be convicted and punished. In a typical criminal case, the state alleges that a defendant has met the parameters of criminal conduct as set forth by a written law, or that the defendant has violated a law that qualifies him for criminal prosecution. Then, the prosecutor, on behalf of the state, presents evidence in order to prove the allegation. The defendant presents his case, and the jury must decide whether the defendant violated the law or met the parameters of criminal conduct as the state alleged.  The judge will give the jury instructions based on the written law to help the jury decide the case. For example, Arizona Revised Statutes 13-1902 explicitly sets out the elements of a robbery. At a robbery prosecution, the jury must essentially decide whether the facts of the case satisfy the elements of the robbery statute.

Personal injury cases are quite different. There are laws relating to personal injury “on the books;” but for the most part personal injury cases revolve around common law. Common law is created by judges through precedent, rather than written out by legislatures and lawmakers. When a jury is set to decide a personal injury case, the judge gives the jury instructions on how to do so that are mostly based on common law. For example, there is no written law that defines negligence for every case. Negligence is a matter of common law. Here’s why that matters:

In most every personal injury claim, the plaintiff must prove fault. Fault is comprised of negligence plus causation. The plaintiff has to prove that the defendant was negligent, and then prove that the defendant’s negligence caused the plaintiff’s injuries.  As already discussed, there is no statutory law that defines negligence. The common law definition is something along the lines of: “failure to use reasonable care in the circumstances.” So, to prove negligence, the plaintiff first has to prove what the standard of care should be in the circumstances, and then prove that the defendant failed to meet that standard. Because it is a matter of common law, the standard of care – and what actions might violate it – vary from case to case.

However, if a personal injury claim is brought under a theory of negligence per se, common law and written statutory law will both be central components of the case. Wth a written law at the center of the case, the negligence per se claim will proceed somewhat like a criminal prosecution case.

The legal doctrine of negligence per se states that a person must be found negligent if he violated the provisions of a written statute, regulation, or code. In other words, you can think of negligence per se as a sort of ‘automatic’ negligence. There is no need to determine the standard of care or a failure to meet the standard of care; negligence will be imputed automatically if the jury finds that a law has been violated. However, only violations of certain laws can lead to negligence per se cases.

Arizona courts have said the following about what sorts of laws can lead to negligence per se cases: First, 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.” (Sources: Good v. City of Glendale, 150 Ariz. 218, 221 (Ct. App. 1986); Griffith v. Valley of the Sun Recovery & Adjustment Bureau, Inc., 126 Ariz. 227, 229 (Ct. App. 1980)). Many of Arizona’s traffic and criminal laws fit into these requirements, and violations of them can lead to negligence per se cases.

If negligence per se does apply, the law in question will be an issue in the case throughout the trial. Much like in a criminal trial, the plaintiff will present evidence that the defendant has violated the elements of the law. At the end of the trial, the judge will instruct the jury on the elements of the law in question and the theory of negligence per se. The judge will tell the jury that if it finds the defendant has violated the law, the jury must also find that the defendant acted negligently.

Remember though that fault is a combination of negligence and causation. Even if negligence per se leads the jury to find that the defendant was negligent, it must still find that the defendant’s negligence caused the plaintiff’s injury before it can award the plaintiff damages. Even in negligence per se cases, causation remains a matter of common law, detached from any written statute. It is an entirely separate issue that the jury must decide. This is why personal injury cases that involve negligence per se are a mix between the worlds of written law and common law.

There is much more to learn about negligence per se. If you wish to learn more, or if you believe your case might involve negligence per se, please give us a call.


This blog should be used for informational purposes only. It does not create an attorney-client relationship with any reader and should not be construed as legal advice. If you need legal advice regarding Negligence Per Se, or any other personal injury, please feel free to contact Brian T. Allen at  480.461.5335,  log on to,  or contact an attorney in your area. Udall Shumway PLC is located in Mesa, Arizona and is a full service law firm. We assist Individuals, families, businesses, schools and municipalities in Mesa and the Phoenix/East Valley.