To win a lawsuit, the victim must prove that defendant was negligent — that is, that he did not exercise "due care." That can be difficult. But it can also be easy, such as when the doctrine of negligence per se comes into play.
When the doctrine of negligence per se applies, defendant’s conduct will presumed to have been negligent with no need for plaintiff to present any further proof. A defendant’s conduct is negligent per se if:
- The conduct violated a statute, ordinance, or regulation;
- The violation caused the injury;
- The statute, ordinance, or regulation was designed to prevent the type of injury that occurred; and
- The person suffering the injury was one of the class of persons for whose protection the statute, ordinance, or regulation was adopted.
The doctrine of negligence per se may apply when a victim is injured on a construction 
site (or even a home remodeling project). For example, if the wrongdoer has violated an OSHA regulation, that may be enough to prove the wrongdoer was negligent. The victim must still show that the violation caused his injury, that the regulation was designed to prevent his type of injury, and that he was of the class of persons for whose protection the statute was adopted. But he need not prove, as he would need to in most cases, that the wrongdoer did not exercise due care.
If a jury determines that a defendant violated a regulation, the defendant can be found negligent per se even if the governmental agency did not charge him with a violation. Therefore, an attorney investigating a client’s case must conduct his own research and investigation into whether the defendant may have violated any applicable statute, ordinance or regulation.