"Juries almost never acquit people by reason of insanity," says
Henry Steadman, who heads Policy Research Associates, a think tank
based in Albany, New York.
number of states returned to a standard borrowed from 19th-century English Law:
the M'Naghten Rule. It demands that a defendant be so out of touch with reality
as to not know his actions were wrong. Being unable to control one's actions is
In the 1980's Steadman did the most authoritative study on the realities of
the insanity defense. In an 8-state study encompassing some one million felony
cases, he found that just under 1% of defendants pled not-guilty-by-reason-of-insanity,
and just one in four of those attempts resulted in an acquittal. His findings
contrasted sharply with the public perception as measured in surveys; Americans
over-estimated the frequency of insanity- defense acquittals by a striking 80
A few decades ago it might have been slightly easier to get an
insanity acquittal than it is today, some experts believe. In the
1960's and 70's about half of the states used a relatively lenient
standard for legal insanity—one that required the defendant to show
she'd been unable to control her criminal behavior because of a
That standard quickly went out of fashion in 1982.
Using a version of the inability-to-control standard, a Washington,
D.C. jury acquitted John W. Hinckley, Jr., who had shot President
Reagan and three aides in a delusional attempt to impress the actress
Jodi Foster, whom he admired from afar. The court sent Hinckley
to a secure mental hospital, where he remains to this day. But politicians
and others expressed outrage at the verdict, and within four years
half the states and the federal government had changed their laws,
making it tougher to be found legally insane.
A number of states returned to a standard borrowed from 19th-century
English Law: the M'Naghten Rule. It demands that a defendant be
so out of touch with reality as to not know his actions were wrong.
Being unable to control one's actions is not enough.
At Kyle Zwack's trial in Houston in 1987, mental health experts
on both sides agreed Kyle was mentally ill. But was he legally insane?
Not Crazy Enough