'insanity defense' and diminished capacity
United States v. Hinckley, a recent successful use of the insanity
On March 30, 1981, John W. Hinckley, Jr., shot President Ronald Reagan,
attempting to assassinate him. His defense attorneys did not dispute that
he had planned and committed the attack. His attorneys instead argued that
he was acting according to the impulses of a diseased or impaired mind.
The legal argument
Hinckley's attorneys argued that Hinckley had not acted of his own volition,
but that his life was controlled by his pathological obsession with the
movie, Taxi Driver, starring Jodie Foster. In that movie, the title
character stalks the president and fights in a shootout. Hinckley's attorneys
said he saw the movie 15 times, and identified with the hero and was seeking
to reenact the events of the movie in his own life.
Hinckley's attorneys argued that Hinckley was schizophrenic. They argued
that the movie was the actual planning force behind the defendant's assassination
attempt against the President.
The judge allowed the defense to introduce evidence, in the form of
a CAT scan, that Hinckley's brain showed signs of shrunken brain tissue,
one of the common symptoms of schizophrenia. The prosecution opposed this
evidence, on the grounds that the technical nature of the evidence would
cause the jury to place too heavy an emphasis on it. The judge rejected
this argument, on the grounds that the evidence was relevant. (See the
law of evidence on admissibility.)