A now-disused term of the common law to refer to a person suffering from a disabling mental disorder.
British Columbia's Patients Property Act now defines what would have been described as, in yesteryear, a lunatic, a person "incapable of managing himself or herself or his or her affairs", and for whom a committee is appointed.
Chapter 9 of the British statute of 1324, cited as 17 Edward II, read as follows:
"The King shall have custody of the lands of natural fools, taking the profits of them without waste or destruction, and shall find them their necessaries of life, of whose Fee forever the lands be holden. And after death of such idiots, he shall render it to the right heirs, so that such idiots shall not aliene nor their heirs shall be disinherited."
England codified the law in 1890 with a 342-section Lunacy Act which, at ¶90, defined a lunatic as a person "of unsound mind and incapable of managing himself or his affairs".
The term was gradually replaced with that of insanity and now, circa 2007, the politically and medically correct word is personality disorder.
Blackstone, in his Commentaries on the Laws of England, (Book 1, Chapter 8, "Of the Rights of Persons"), comprehensively covered the topic as follows, and as the law was in the mid-1800s:
"An idiot, or natural fool, is one that has had no understanding from his nativity; and therefore is by law presumed never likely to attain any, for which reason the custody of him and of his lands was formerly vested in the lord of the fee; (and therefore still, by special custom, in some manors the lord shall have the ordering of idiot and lunatic copyholders) but, by reason of the manifold abuses of this power by subjects, it was at last provided by common consent, that it should be given to the king, as the general conservator of his people, in order to prevent the idiot from wasting his estate, and reducing himself and his heirs to poverty and distress: This fiscal prerogative of the king is declared in parliament by statute 17 Edw. II. c. 9.
"By the old common law there is a writ de idiota inquirendo, to enquire whether a man be an idiot or not, which must be tried by a jury of twelve men, and if they find him purus idiota, the profits of his lands, and the custody of his person may be granted by the king to some subject, who has interest enough to obtain them.
"This branch of the revenue has been long considered as a hardship upon private families; and so long ago as in the 8 Jac. I. it was under the consideration of parliament, to vest this custody in the relations of the party, and to settle an equivalent on the crown in lieu of it; it being then proposed to share the same fate with the slavery of the feodal tenures, which has been since abolished. Yet few instances can be given of the oppressive exertion of it, since it seldom happens that a jury finds a man an idiot a nativitate, but only non compos mentis from some particular time; which has an operation very different in point of law.
"A man is not an idiot, if he has any glimmering of reason, so that he can tell his parents, his age, or the like common matters. But a man who is born deaf, dumb and blind, is looked upon by the law as in the same state with an idiot, he being supposed incapable of understanding, as wanting those senses which furnish the human mind with ideas.
"A lunatic, or non compos mentis, is one who has had understanding, but by disease, grief, or other accident has lost the use of his reason. A lunatic is indeed properly one that has lucid intervals; sometimes enjoying his senses, and sometimes not, and that frequently depending upon the change of the moon.
"But under the general name of non compos mentis (which Sir Edward Coke says is the most legal name) are comprised not only lunatics, but persons under frenzies; or who lose their intellects by disease; those that grow deaf, dumb, and blind, not being born so; or such, in short, as are by any means rendered incapable of conducting their own affairs. To these also, as well as idiots, the king is guardian, but to a very different purpose. For the law always imagines, that these accidental misfortunes may be removed; and therefore only constitutes the crown a trustee for the unfortunate persons, to protect their property, and to account to them for all profits received, if they recover, or after their decease to their representatives.
"And therefore it is declared by the statute 17 Edw. II. c. 10 that the king shall provide for the custody and suftentation of lunatics, and preserve their lands and the profits of them, for their use, when they come to their right mind: and the king shall take nothing to his own use; and if the parties die in such estate, the residue shall be distributed for their souls by the advice of the ordinary, and of course (by the subsequent amendments of the law of administrations) shall now go to their executors or administrators."