Negligence claims generally involve carelessness in taking an action, or failing to act, and require: (1) a legal duty owed by one person to another; (2) a breach of that duty; and (3) damages (injury) proximately caused by the breach.

Proximate cause has two components: (1) foreseeability and (2) cause-in-fact. Foreseeability requires that a person of ordinary intelligence should have reasonably anticipated the danger created by a negligent act or omission. Foreseeability is not measured by hindsight, but instead by what the actor knew or should have known at the time of the alleged negligence. Foreseeability requires only that the general danger, not the exact sequence of events that produced the harm, be foreseeable.

For a negligent act or omission to have been a cause-in-fact of the harm, the act or omission must have been a substantial factor in bringing about the harm, and absent the act or omission—i.e., but for the act or omission—the harm would not have occurred. If the defendant's negligence merely furnished a condition that made the injuries possible, there can be no cause in fact. There may be more than one proximate cause of an occurrence.

Negligence claims (a negligence cause of action) have long been recognized by judges in court opinions, and usually derive their authority from this common law, rather than from statutes enacted by state legislatures.

In California, negligence claims are based on common law principles rather than specific statutes. To establish a negligence claim, a plaintiff must prove that the defendant owed them a legal duty of care, breached that duty, and that the breach was the proximate cause of their damages. Proximate cause includes both foreseeability and cause-in-fact. Foreseeability means that a person of ordinary intelligence should have anticipated the danger their actions or inactions could create, focusing on what was known or should have been known at the time, not in hindsight. The danger itself must have been foreseeable, not the specific sequence of events. Cause-in-fact requires that the defendant's act or omission was a substantial factor in causing the harm, and that the harm would not have occurred 'but for' the defendant's negligence. If the negligence only created a condition that allowed the harm to occur, it is not considered a cause-in-fact. There can be multiple proximate causes for an event. These principles are derived from judicial decisions over time and are applied by courts to assess liability in negligence cases.