from tort.laws.com: Negligence used to be a much broader term that referred to any sort of breach of the peace, but has evolved over time to become a separate entity from intentional torts as well as strict liability torts. The concept first appeared in regards to professional community members, such as doctors or blacksmiths, who possessed a certain duty to the community to provide honest service. If this duty was breached, the individual was guilty of negligence.
Unavoidable Accident: An unavoidable accident occurs when, despite all exercise of reasonable care, the defendant could not have foreseen or possibly avoided the resulting harm to the plaintiff. In order for an accident to be unavoidable, the situation must in no way be caused by or added to by the defendant.

Unless some evidence can be found that proves the defendant should have reasonably been aware that this accident would occur, he is not liable for the plaintiff's injuries. It must be proven that there was no wrongful intent on behalf of the defendant. This is only used in unique instances where the circumstances of the case prove that the plaintiff's injuries were absolutely unavoidable.

Elements of Cause of Action: There are certain elements that are required to prove that a defendant acted negligently. There is a specific code of conduct which all people are expected to follow and there is a duty of the public to act in a certain way which reduces the risk of harm to others.

Negligence can only be claimed by an injured plaintiff whose interests have actually been interfered with, meaning that a plaintiff must prove his injuries, and prove that they were caused by the defendant. This proximate cause is the link between the defendant's actions and the plaintiff's injuries. There is a statute of limitations in negligence cases. However there are several rules, such as discovery and continuing negligence, which may excuse a plaintiff from the statute of limitations.