The reasonable person is a legal fiction of the common law representing an objective standard against which any individual's conduct can be measured. It is used to determine if a breach of the standard of care has occurred, provided a duty of care can be proven.

The reasonable person standard holds: each person owes a duty to behave as a reasonable person would under the same or similar circumstances.[1][2] While the specific circumstances of each case will require varying kinds of conduct and degrees of care, the reasonable person standard undergoes no variation itself.[3][4]

This standard performs a crucial role in determining negligence in both criminal law—that is, criminal negligence—and tort law. The standard also has a presence in contract law, though its use there is substantially different.

The standard does not exist independently of other circumstances within a case which could affect an individual's judgment.

History

The first appearance of the reasonable person standard was in the English case of Vaughan v. Menlove (1837).[5] In Menlove, the defendant had stacked hay on his rental property in a manner prone to spontaneous ignition. After repeated warnings over the course of five weeks, the hay ignited and burned the defendant's barns and stable, and then spread to the landlord's two cottages on the adjacent property. Menlove's attorney admitted his client's "misfortune of not possessing the highest order of intelligence," arguing that negligence should only be found if the jury decided Menlove had not acted with "bona fide [and] to the best of his [own] judgment."

The Menlove court disagreed, reasoning that such a standard would be too subjective, instead preferring to set an objective standard by which to adjudicate cases:

The care taken by a prudent man has always been the rule laid down; and as to the supposed difficulty of applying it, a jury has always been able to say, whether, taking that rule as their guide, there has been negligence on the occasion in question. Instead, therefore, of saying that the liability for negligence should be co-extensive with the judgment of each individual, which would be as variable as the length of the foot of each individual, we ought rather to adhere to the rule which requires in all cases a regard to caution such as a man of ordinary prudence would observe. That was, in substance, the criterion presented to the jury in this case and, therefore, the present rule must be discharged.

English courts upheld the standard again nearly 20 years later in Blyth v. Company Proprietors of the Birmingham Water Works,[6] holding:

Negligence is the omission to do something which a reasonable man, guided upon those considerations which ordinarily regulate the conduct of human affairs, would do, or doing something which a prudent and reasonable man would not do.

Rationale

American jurist Oliver Wendell Holmes, Jr. explained the theory behind the reasonable person standard as stemming from the impossibility of "measuring a man's powers and limitations."[7] Individual, personal quirks inadvertently injuring the persons or property of others are no less damaging than intentional acts. In order for society to function, "a certain average of conduct, a sacrifice of individual peculiarities going beyond a certain point, is necessary to the general welfare."[7] Thus, a reasonable application of the law is sought, compatible with planning, working, or getting along with others. As such, "his neighbors accordingly require him, at his proper peril, to come up to their standard, and the courts which they establish decline to take his personal equation into account."[7]

The reasonable person standard is by no means democratic in its scope; it is, contrary to popular conception, intentionally distinct from that of the "average person," who is not necessarily guaranteed to always be reasonable.[8] The reasonable person will weigh all of the following factors before acting:

• the foreseeable risk of harm his actions create versus the utility of his actions;
• the extent of the risk so created;
• the likelihood such risk will actually cause harm to others;
• any alternatives of lesser risk, and the costs of those alternatives.

Taking such actions requires the reasonable person to be appropriately informed, capable, aware of the law, and fair-minded. Such a person might do something extraordinary in certain circumstances, but whatever that person does or thinks, it is always reasonable.

The reasonable person has been called an "excellent but odious character."[9]

He is an ideal, a standard, the embodiment of all those qualities which we demand of the good citizen ... [he] invariably looks where he is going, ... is careful to examine the immediate foreground before he executes a leap or bound; ... neither stargazes nor is lost in meditation when approaching trapdoors or the margins of a dock; ... never mounts a moving [bus] and does not alight from any car while the train is in motion, ... uses nothing except in moderation, and even flogs his child in meditating only on the golden mean.[10]

English legal scholar Percy Henry Winfield summarized much of the literature by observing that:

[H]e has not the courage of Achilles, the wisdom of Ulysses or the strength of Hercules, nor has he the prophetic vision of a clairvoyant. He will not anticipate folly in all its forms but he never puts out of consideration the teachings of experience shows such negligence and so will guard against negligence of others when experience shows such negligence to be common. He is a reasonable man but not a perfect citizen, nor a "paragon of circumspection. ..."[11]

Hand Rule

Under American common law, a well known—though nonbinding—test for determining how a reasonable person might weigh the criteria listed above was set down in United States v. Carroll Towing Co.[12] by the Chief Justice of the Second Circuit Court, Learned Hand. The case concerned a barge that had broken her mooring with the dock. Writing for the court, Hand held:

[T]he owner's duty, as in other similar situations, to provide against resulting injuries is a function of three variables: (1) The probability that she will break away; (2) the gravity of the resulting injury, if she does; (3) the burden of adequate precautions.

While the test offered by Hand does not encompass all of the criteria available above, juries in a negligence case might well still be instructed to take the other factors into consideration in order to determine whether the defendant was negligent.[13]

Personal circumstances

While the legal fiction of the reasonable person represents the ideal human actor, one would be hard pressed to characterize any individual human as meeting the standard, whether in whole or in part, all of the time. Since some human actors have limitations, the standard only requires that people act similarly to how "a reasonable person under the circumstance" would, as if their limitations were themselves circumstances. As such, courts require that the reasonable person be viewed as experiencing the same limitations as the defendant.