M’NAGHTENSTANDARD
The M’Naghten Standard is a legal test to guide juries
and courts in their determination of whether a defen-
dant should be found not guilty by reason of insanity.
Although defendants were acquitted for crimes they
committed while they were legally insane for cen-
turies before the M’Naghten Standard was estab-
lished, no uniform legal test was adopted by the courts
until the middle of the 19th century following the case
of Daniel M’Naghten (Regina v. M’Naghten,1843).
Daniel M’Naghten was acquitted for killing the
private secretary of the Prime Minister of England, Sir
Robert Peel. Mr. M’Naghten had a mental illness that
was most likely a form of paranoid schizophrenia. His
mental illness was characterized by the belief that he
was the victim of an international conspiracy. He
believed that if he killed the prime minister, it would
lead to the second coming of Christ and the salvation
of humanity. Rather than shooting the prime minister,
though, he mistakenly shot his private secretary,
Edward Drummond, who died a few days later. After
he shot Mr. Drummond, he attempted to fire a second
shot, but he was apprehended and arrested.
Daniel M’Naghten’s father was able to secure a
well-financed defense led by a leading barrister of the
day. The central issue in M’Naghten’s case was the
proper standard for establishing a legal defense of
insanity. M’Naghten was apparently only “partly
insane,” and purportedly suffered from delusions con-
cerning politics. Apart from his specific paranoid
beliefs, he was able to make plans and was able to live
in the society. At the trial, his barristers argued that he
should be found not guilty by reason of insanity. The
jury acquitted Daniel M’Naghten because of his
insanity. M’Naghten was committed to Bethlem and,
later, Broadmoor Mental Institution, where he died
approximately at the age 50 on May 3, 1865, some 20
years following his trial.
As soon as the verdict in the M’Naghtencase was
announced, the public became alarmed that insane
people could kill without fear of punishment. In addi-
tion to the concern the public showed, Queen Victoria
(who herself had been the target of would-be assassins
on several occasions) and members of the House of
Lords also made their disapproval of the verdict known.
Just over 2 months after the decision in M’Naghten
was made public, 15 common law judges in GreatBritain were summoned to the House of Lords to help
determine the proper standard for criminal responsibil-
ity of the criminally insane. Fourteen of the judges
agreed that essentially the same standard employed in
M’Naghtenwas the correct legal standard. The opinion
delivered included the language pertaining to the legal
test of insanity, known as the M’Naghten Standard:A person is presumed sane unless it can be clearly
proven that, at the time of the committing of the act,
the party accused was labouring under such a defect of
reason, from disease of the mind, as not to know the
nature and quality of the act he was doing; or, if he did
know it, that he did not know he was doing what was
wrong. The mode of putting the latter part of the ques-
tion to the jury...had generally been,whether the
accused at the time of doing the act knew the differ-
ence between right and wrong.(Regina v. M’Naghten,
1843, 10 Cl. & Fin. At 203, 8 Eng. Rep. at 720)A person labouring under a “partial delusion only,
and [who] is not in other respects insane...must be
considered in the same situation, as to responsibility,
as if the facts, in respect to which the delusion exists,
were real.” (Regina v. M’Naghten,1843, 10 Cl. &
Fin. At 203, 8 Eng. Rep. at 723)There are three significant substantive elements of
the M’Naghten Standard. First, the decision maker
must determine that the defendant was suffering from
“a defect of reason, from disease of the mind.” Today,
these words are interpreted to mean that the defendant
is suffering from a mental disorder. Next, the decision
maker must decide whether the evidence shows that
the defendant did not “know” the “nature and quality
of the act he was doing.” Thus, the defendant must not
have understoodexactly what he or she did. Finally,
the M’Naghten Standard also requires an inquiry to
determine whether the defendant knew “what he was
doing was wrong.” Therefore, the defendant who
understands his or her act, yet does not have the capa-
bility of knowing that the act was wrong, may also be
acquitted under the M’Naghten test. Because the final
two elements require a subjective exploration of the
defendant’s thinking, the M’Naghten test is referred to
as a “cognitive” test of insanity. It is also known as the
“Right/Wrong Test” since it focuses on an enquiry of
the defendant’s capacity, at the time of the offense, to
be able to know right from wrong.M’Naghten Standard——— 511M-Cutler (Encyc)-45463.qxd 11/18/2007 12:43 PM Page 511