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Negligence is the failure to behave with the level of care that a reasonable person would have exercised under the same circumstances. Either a person’s actions or omissions of actions can be found negligent. The omission of actions is considered negligent only when the person had a duty to act (e.g., a duty to help someone because of one’s own previous conduct).

Negligence is a foundational concept of tort law. Some primary factors to consider in ascertaining whether a person’s conduct lacks reasonable care are the foreseeable likelihood that the conduct would result in harm, the foreseeable severity of the harm, and the burden of precautions necessary to eliminate or reduce the risk of harm. The following five elements may typically be required to prove negligence:

  • The existence of a legal duty that the defendant owed the plaintiff
  • Defendant’s breach of that duty
  • Harm to the plaintiff
  • Defendant’s actions are the proximate cause of harm to the plaintiff
  • Defendant’s actions are the cause-in-fact of harm to the plaintiff

Legal Duty of Care

Generally, members of society have entered a social contract that includes a duty to not cause harm to others. When considering legal duty as an element of negligence, there is a duty to act reasonably. When a jury is asked to determine if a defendant’s actions were reasonable, the standard is what a reasonable person would have done in the defendant’s situation. The following is a non-exhaustive list of ways to determine if the defendant owed a duty of care to the plaintiff:

  • The defendant engaged in the creation of risk which resulted in the plaintiff’s harm
  • Voluntary undertaking: the defendant volunteered to protect the plaintiff from harm, possibly preventing others from protecting the plaintiff
  • Knowledge: the defendant knows or should know that their conduct will harm the plaintiff
  • Business/voluntary relationships: certain relationships—such as business owner and customer, innkeeper and guest, landowner and lessee, doctor and patient—create duties of care

Breach of Duty of Care

Some courts in the United States use the Hand Formula (created by Judge Learned Hand in United States v. Carroll Towing) to determine if there was a breach of the duty of care to the plaintiff.

  • If B < PL, then the defendant breached the duty of care.
    • B=burden of taking precautions
    • P=probability of loss
    • L=severity of loss (personal loss, not societal loss)

If the burden of taking such precautions is less than the probability of injury multiplied by the severity of the resulting injury, then the defending party breached their duty of care to the plaintiff and may be liable for the plaintiff’s injuries, if the remaining elements of negligence can be proven.

This formula considers economic costs to the defendant in its approach to assessing liability. The idea is not to eliminate the risk of harm entirely, for complete elimination of risk would result in a high economical burden for the defendant that would then trickle down to costs for the consumer. Instead, the defendant is encouraged to take precautions that reduce either the probability of harm or severity of possible harm, such that their burden is less than the probability of harm multiplied by the severity of potential harm.

Harm to the Plaintiff

Typically, harm to the plaintiff must be either bodily harm or harm to property (personal property or real property). Harm that is solely economic usually will not satisfy this element in proving negligence. Some states recognize emotional distress as harm to the plaintiff, even if the harm is purely mental and not physical.

Proximate Cause

To satisfy proximate cause, the defendant’s breach of the duty of care must be the actual cause of the harm to the plaintiff. One way to assess proximate cause is to evaluate the foreseeability of the defendant’s actions resulting in harm. For example, if the defendant throws a rock off of their balcony of a high-rise building without looking, and the rock strikes the plaintiff walking on the sidewalk below, the defendant’s actions are the proximate cause of the plaintiff’s injury because the defendant should have foreseen the possibility that the rock could hit someone below them.

Plaintiff conduct and intervening factors can also affect the analysis of proximate cause. If a plaintiff is engaging in conduct that increases the likelihood of harm, the defendant’s conduct may not be ruled as the proximate cause of that harm. Likewise, if the defendant acts unreasonably, but an intervening factor such as a third party steps in and contributes to the plaintiff’s injury, the defendant may not be liable.


Cause-in-fact is the final element in the negligence analysis and is often the easiest to prove. For this element, the jury needs to consider if the plaintiff’s harm would not have occurred but for the defendant’s conduct. Unlike proximate cause, intervening factors play less of a role in establishing cause-in-fact. If the defendant’s actions sets off a string of subsequent occurrences that lead to injury to the plaintiff, and none of those events would have occurred but for the defendant’s initial actions, then the defendant’s conduct is considered the cause-in-fact of harm to the plaintiff.

[Last updated in July of 2023 by the Wex Definitions Team]