Reasonable Person Test

What is a Reasonable Person ?

The reasonable person test is a legal concept used in UK law, which seeks to establish a standard of conduct that a hypothetical reasonable person would exhibit in a given situation. It is also known as the objective standard test or the reasonable man/woman test.

What is the Reasonable Person Test ?

The Reasonable Person test is used to determine whether a defendant has breached their duty of care in a particular situation, for example, in negligence cases. The court asks what a reasonable person would have done in the same circumstances, taking into account the defendant’s knowledge and experience at the time of the incident.

The test was developed in response to the need for a standard to measure the conduct of individuals in society. It was seen as a way to ensure that people acted reasonably in their interactions with others and did not cause harm through their actions.

History of the Reasonable Person Test

The history of the reasonable person test began in the old English law and was first used in a civil lawsuit Vaughn v. Menlove in 1837.

The defendant had stacked hay on his rental property in a manner prone to spontaneous ignition. This was despite being repeatedly warned about the danger over the course of five weeks.

This determined that a reasonable person would not have stacked hay in a dangerous manner next to a neighbours’ structure (as the defendant in that case did) because of the risk of fire.

The Man on the Clapham Omnibus is a hypothetical ordinary and reasonable person used by the courts in English law where it is necessary to decide whether a party has acted as a reasonable person would.

The phrase was reportedly first put to legal use in a judgment by Sir Richard Henn Collins MR in the 1903 English Court of Appeal libel case, McQuire v. Western Morning News


Over time, the reasonable person test has been refined and adapted to suit different legal contexts.

In the UK, the test is now a fundamental principle of negligence law and is used extensively in other areas of law, such as criminal law, family law and contract law.

In practice, the test is used by judges and juries to evaluate the conduct of defendants and to determine whether they have acted in a reasonable manner.

The test is a flexible one, which takes into account the particular circumstances of each case. This means that the standard of conduct required of the reasonable person may vary depending on the situation.


Overall, the reasonable person test is an important legal concept that helps to ensure that people act reasonably and with due care in their interactions with others. It is a key component of UK law and is used extensively in legal proceedings.

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