When John Hinckley was on trial for his 1981 assassination attempt on US President Ronald Reagan, his defence team wanted to use an insanity defence. The insanity defence was used in fewer than 2% of criminal trials and was unsuccessful in three out of every four attempts. They used an expert witness in an attempt to demonstrate that Hinckley was likely to be schizophrenic (the basis of their insanity plea). Dr. Daniel R. Weinberger, psychiatrist for the National Institute of Mental Health, testified that:

30% of CAT scans on schizophrenic people show brain atrophy (shrinkage); Only 2% of scans on non-schizophrenics show atrophy. Defence lawyer Gregory B. Craig wanted to introduce a CAT scan of Hinckley, which showed brain atrophy.

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