In English-speaking common-law jurisdiction, John Doe is used for a defendant in a legal example or for a person whose identity is unknown or is intended to be anonymous. Male corpses whose identity is unknown are also known by the name John Doe. A female who is not known is referred to as Jane Doe. An anonymous plaintiff is known as Richard Roe.
The Oxford English Dictionary states says that John Doe is "the name given to the fictitious lessee of the plaintiff, in the (now obsolete) mixed action of ejectment, the fictitious defendant being called Richard Roe.
An of the reasons why a fictitious tenant and a fictitious defendant were named is found in Charles Rembar's book The Law of the Land.
By extension from the law usage, John Doe is often used in computer software needing a default or example first and last name for a form.
