Forensic Psychology : Not Guilty By Reason of Insanity - Some Statistics
Posted Oct 03 2008 12:51pm
Here’s a brief post on the numbers of insanity defense. It’s not used very much, and when it is used, it isn’t very successful. Statistics suggest the plea of NGRI is used in 1% or less of all criminal cases, and when it is used, it is only successful about 25% of the time. In fact, the second number seems high to me, but that is because, as I’ve previously mentioned, I work in the Federal system, which has a higher standard.
In general, the insanity plea gets so much attention for two reasons, in my opinion. First, because of the high profile nature of some recent crimes where the defendant has pled NGRI, including several successful pleas. For example, John Hinckley Jr. was found to be NGRI, and more recently the Andrea Yates trial drew attention to the issue. Second, the finding of NGRI is so profound, compared to a finding of, say, being incompetent. If a person is found to be incompetent to stand trial, their trial does not end - they are afforded a period of time for restoration to competency. On the other hand, there is a widespread belief someone who is found NGRI is “getting off.” In fact, while their legal culpability ends, they very well may end up hospitalized for a significant period of time.
Two other items of note. Generally speaking, NGRI is not used solely in high notoriety cases such as murder. In fact, murder charges account for only one third of cases where the defendant pleads NGRI, they fare no better than anyone else in terms of success rate. Second, as forensic psychology has improved, and continues to improve, in terms of completing evaluations such as these (and I believe they have, though there is still much more to learn), the correct verdict is more often determined. That is, it is becoming significantly more difficult for individuals to fake serious mental illness effectively, no matter what Hollywood and television would have you believe. Individuals who are found NGRI are, generally speaking, going to be individuals with severe mental health issues. Unlike the days of the “Twinkie Defense,” the defendants of today benefit far more (as does society) by providing them treatment rather than incarceration.