Reasonable person

The "reasonable man" appeared in Richard Hooker's defence of conservatism in religion, the Laws of Ecclesiastical Polity (1594-7), where he preferred Papists to Turks and accepted the opinions of religious experts when there was no reason to dissent.[14]

In 1835, Adolphe Quetelet detailed the characteristics of l'homme moyen (French, "average man"). His work is translated into English several ways. As a result, some authors pick "average man", "common man", "reasonable man", or stick to the original "l'homme moyen". Quetelet was a Belgian astronomer, mathematician, statistician and sociologist. He documented the physical characteristics of man on a statistical basis and discussed man's motivations when acting in society.[15]

Two years later, the "reasonable person" made his first appearance in the English case of Vaughan v. Menlove (1837).[16] In Menlove, the defendant had stacked hay on his rental property in a manner prone to spontaneous ignition. After he had been repeatedly warned 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 for adjudicating 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,[17] 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.

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."[18] Individual, personal quirks inadvertently injuring the persons or property of others are no less damaging than intentional acts. 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."[18] 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."[18] He heralded the reasonable person as a legal fiction whose care conduct under any common set of facts, is chosen—or "learned" permitting there is a compelling consensus of public opinion—by the courts.[4][5]

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.[19] 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."[20]

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.[21]

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 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. ..."[22]

Under United States 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.[23] in 1947 by the Chief Judge of the U.S. Court of Appeals for the Second Circuit, Learned Hand. The case concerned a barge that had broken her mooring with the dock. Writing for the court, Hand said:

[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 the criteria available above, juries in a negligence case might well still be instructed to take the other factors into consideration in determining whether the defendant was negligent.[24]

The Sedona Conference issued its Commentary on a Reasonable Security Test to advance the Hand Rule for a cybersecurity context. The commentary adds three important articulations to the Hand Rule; a person is reasonable if no alternative safeguard would have provided an added benefit that was greater than the added burden, the utility of the risk should be considered as a factor in the calculation (as either a cost or a benefit, depending on the situation), and both qualitative and quantitative factors may be used in the test.[25]

The legal fiction[3] of the reasonable person is an ideal, as nobody is perfect. Everyone has limitations , so the standard requires only that people act similarly to how "a reasonable person under the circumstances" would, as if their limitations were themselves circumstances. As such, courts require that the reasonable person be viewed as having the same limitations as the defendant.

For example, a disabled defendant is held to a standard that, by necessity, represents how a reasonable person with that same disability would act.[26] This is no excuse for poor judgment, or trying to act beyond one's abilities. Were it so, there would be as many standards as there were defendants; and courts would spend innumerable hours, and the parties much more money, on determining that particular defendant's reasonableness, character, and intelligence.

By using the reasonable person standard, courts instead use an objective tool and avoid such subjective evaluations. The result is a standard that allows the law to behave in a uniform, foreseeable, and neutral manner when attempting to determine liability.

Factors beyond the defendant's control are always relevant. Additionally, so is the context within which each action is made. Many things affect how a person acts: individual perceptions, knowledge, the weather, etc. The standard of care required depends on the circumstances, but is always that which is reasonable.[38]

While community customs may be relied upon to indicate what kind of action is expected in the circumstances, these are not themselves conclusive of what a reasonable person would do.[19][39]

It is precisely for this wide-ranging variety of possible facts that the reasonable person standard is so broad (and often confusing and difficult to apply). However, a few general areas of relevant circumstances rise above the others.

For common law contracts, disputes over contract formation are subjected to what is known as the objective test of assent in order to determine whether a contract exists. This standard is also known as the officious bystander, reasonable bystander, reasonable third party, or reasonable person in the position of the party.[46] This is in contrast to the subjective test employed in most civil law jurisdictions. The test stems from attempts to balance the competing interests of the judicial policies of assent and of reliability. The former holds that no person ought to be contractually obligated if they did not consent to such an agreement; the latter holds that if no person can rely on actions or words demonstrating consent, then the whole system of commercial exchange will ultimately collapse.[47]

Prior to the 19th century, courts used a test of subjective evaluation;[47] that is, the trier of fact determined each party's understanding.[48] If both parties were of the same mind and understanding on matters, then assent was manifested and the contract was valid. Between the 19th and 20th centuries, the courts shifted toward the objectivist test, reasoning that subjective testimony was often unreliable and self-serving.[47]

From those opposite principles, modern law has found its way to a rough middle ground, though it still shows a strong bias toward the objective test.[46] Promises and agreements are reached through manifestations of consent, and parties are liable for actions that deliberately manifest such consent; however, evidence of either party's state of mind can be used to determine the context of the manifestation if said evidence is reliable and compatible with the manifestation in question, though such evidence is typically given very little weight.[48]

Another circumstance where the reasonable bystander test is used occurs when one party has inadvertently misstated the terms of the contract, and the other party sues to enforce those terms: if it would have been clear to a reasonable bystander that a mistake had been made, then the contract is voidable by the party who made the error; otherwise, the contract is binding.