An interesting tidbit on that report, which I think I saw via a link from the Volokh Conspiracy legal blog, is this: the total fraction of the population either locked up in jail, or in a mental hospital, has been relatively constant over the past 100 years.

More than fifty years ago, it was something like 75% mental, 25% prison, while today it is 95% prison, 5% mental, but the fraction of 1 in 100 has been relatively constant, except for a dip from the 1960s through 1980s as the fraction in mental hospitals went down first, then the prisons share went up with a bit of a lag.

It may only be a coincidence as the populations aren't the same. The prison population is very strongly skewed towards young males, and towards minorities (blacks especially), whereas the mental hospital population was more representative. It's not a simple transfer. But still, it's interesting that the rate has been so constant.

Certainly, my girfriend the defense attorney would note (and so would most prosecutors) that a huge percentage of the people they see in the system have some sort of mental deficency, ranging from mild retardation to various behavioral disorders.

(there is slight selection bias in the jail population -- a smart criminal, with no substance additions or emotional disorders, is far less likely to be caught. Almost any of us at HZ could be successful drug kingpins if we wanted to do so)