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involves both action and intention: To be criminally responsible means that a de-
fendant’s crime was the product of both an action or attempted action (the alleged
criminal behavior) and his or her intentionto perform that action (Greene et al.,
2007; Meyer & Weaver, 2006).
After a crime has been committed and a person has been arrested, the legal
system provides two discrete opportunities to determine whether the defendant is
suffering from a mental illness: (1) What was the defendant’s mental state at the time
he or she (allegedly) committed the act? Might the insanity defense be appropriate?
(2) What is the defendant’s mental state during the time of assessment, leading up to
the trial? Can the person adequately assist in his or her own defense? Is the person
competent to stand trial? We next discuss each of these circumstances in turn.While Committing the Crime: Sane or Insane?
In the United States, the legal defi nition of insanity corresponds to a “test” that is
used to determine whether a person is insane. The particular test has changed over
time. In the following sections we review the fi ve tests of insanity that have been
used, beginning with the fi rst—the M’Naghten test.The M’Naghten Test
In England in 1841, a Scottish man named Daniel M’Naghten believed that the
British Prime Minister, Sir Robert Peel, was personally responsible for M’Naghten’s
woes. M’Naghten attempted to shoot Peel, but missed him and killed Peel’s secre-
tary. During M’Naghten’s trial, witnesses testifi ed that he was insane, and the jury
found him not guilty by reason of insanity (NGBI). This verdict did not sit well
with Queen Victoria, reigning monarch at the time, who had been the intended
victim of a number of assassination attempts; she asked that it be reviewed. In re-
sponse, the judges narrowed the insanity defense by limiting the relevance of the
defendant’s mental state to the time the alleged crime was committed. In what came
to be known as the M’Naghten test (or rule), the question asked at a trial became
whether, at the time of committing the act, the defendant knew what he or she was
doing and, if so, knew that the act was wrong—and if he or she did not know this,
it was because of “a defect of reason, from disease of the mind.” With this narrower
test, the judges reversed the verdict and found M’Naghten guilty.The Irresistible Impulse Test
The M’Naghten test of insanity was adopted in the United States and continued to
be used until 1886, when the defi nition of insanity was widened. The new defi ni-
tion, specifi ed by the irresistible impulse test, focused on whether the defendant
knew that the criminal behavior was wrong but nonetheless performed it because of
an irresistible impulse.
Since the irresistible impulse test was introduced, changes in the legal defi nition
of insanity have centered around the extent to which the criminal behavior was
“uncontrollable”; that is, someone might know that the behavior was wrong but
nevertheless be unable to stop it (Parsons v. Alabama, 1886).The Durham Test
In 1954, the Supreme Court ruled on a case, Durham v. U.S., and again broad-
ened the test for the insanity defense. The Durham test was designed to determine
whether the irresistible impulse was due to mental defect or disorder present at the
time of the alleged crime. The Durham ruling shifted the insanity defense so that it
hinged on evidence that the behavior did not arise entirely from free will. The Dur-
ham ruling moved away from consideration about morality (knowing “right from
wrong”) and into the realm of science (having a mental impairment).
There was major drawback to the Durham ruling, however: It left unclear what
constituted a mental defect or disorder. For instance, it is possible that someone
who was drunk at the time that a crime was committed might be considered toThe earliest insanity defense case was that of
Daniel M’Naghten, a Scottish man whose delu-
sions about the British Prime Minister led him,
in 1841, to commit murder. After M’Naghten was
found not guilty by reason of insanity, the House
of Lords narrowed the criteria for determining
insanity; these criteria came to be known as the
M’Naghten test.
The Granger Collection, New York
Criminally responsible
The determination that a defendant’s
crime was the product of both an action
or attempted action (the alleged criminal
behavior) and his or her intention to perform
that action.
M’Naghten test (or rule)
The legal test in which a person is considered
insane if, because of a “defect of reason,
from disease of the mind,” he or she did not
know what he or she was doing (at the time
of committing the act) and did not know that
it was wrong.