Psychopaths have been a hot topic amongst philosophers, psychologists, and legal scholars for over a decade. Even so, no consensus has emerged regarding their criminal culpability. For example, legal scholar Stephen Morse has argued that the psychopath's emotional defects means he should be considered legally insane. Heidi Maibom and Walter Glannon, on the other hand, have claimed that psychopath's deficits do not qualify them for the insanity defense (although they may warrant partial mitigation of culpability).
Meanwhile, upwards of 25% of the prison population may qualify as psychopaths using the well-established Hare PCL-R checklist. This is some evidence that the courts do not consider psychopathy as an excusing condition. This recent article in the Guardian about the Sandyhook school shootings provides a hint as to why. The author sounds outraged that people are attempting to "medicalize" the Sandyhook shooter. Instead of thinking that he is "sick", the author says we should feel free to believe that Adam Lanza is just plain evil, and deserves our most severe punishments.
Similar claims have been made about psychopathy: that the diagnoses represents "medicalization" of evil. Recently I asked defense attorney Ken Murray, who has tried dozens of capital cases, whether he had ever introduced evidence of psychopathy as mitigation in the sentencing phrase of a capital trial. He was aghast at the idea. I asked this because in one of our last capital trials in Illinois (before the death penalty was abolished), the defense for Brian Dugan brought in Kent Kiehl, a cognitive neuroscientist, during sentencing to present neuroscientific evidence of psychopathy by showing low levels of activation in the paralimbic system (where emotional responses are thought to be generated).
The move seemed to backfire, and the jury sentenced Dugan to death. Ken said the introduction of evidence of psychopathy was probably a last resort, as good defense attorneys know the condition is more likely to trigger the notion that the defendant is evil and dangerous than a mitigating assessment of diminished mental capacity. One can imagine a juror saying to herself, "that picture proves his brain is evil!"
The crux of the problem is this: psychological diagnoses and neuroscientific evidence of psychopathy cannot comment upon a defendant's culpability until they can be understood to interact with the folk notions of responsibility attribution in a reliable way. As Nicole Vincent says: "Neurological conditions do not undermine responsibility simply by virtue of being disorders, but rather they do so in virtue of the effect they have on our mental capacities...which are required for moral agency." Under the M'Naghten rule, the defense of legal insanity requires that a defendant, due to mental illness, not know the nature and quality of his act, or if he did know, not know what he was doing was wrong. Scientific evidence that a schizophrenic was acting under a hallucination, for example, may indicate he didn't understand the nature of his act.
The reason why scholars are split on whether psychopathy is that it isn't clear whether lack of appropriate emotional states means a psychopath fails to understand the nature and quality of his act. Psychopaths who commit violent crimes usually know that they are causing harm. They just don't care.
In a recent article, Bill Hirstein and I argued that at least some psychopaths are like someone who is colorblind. Colorblind drivers lack information important for action: color information, which is important, for example, when determining whether to stop or go at a traffic light. However, this lack does not excuse the colorblind driver who runs a red light. The burden is on her to compensate for her lack (to learn the relative positions of the lights).
Psychopaths often have higher than normal IQs, and some even have higher than normal executive function. Executive functioning, which happens in the pre-frontal cortex of the brain and employs higher-order reasoning processes, allows for non-routine planning and execution of actions. We argue that psychopaths with intact executive functions, like colorblind drivers, should be required to use their reasoning processes to compensate for their emotional deficits. We know this can be done, because high-functioning autistics, who also suffer from emotional deficits, often employ rule-following to keep themselves from offending or harming others.
Some psychopaths, however, seem to have lower than normal executive function, and as a result may have problems with atttention and impulsivity, in addition to their emotional deficits. It is possible that these psychopaths, while not so impaired as to lack an understanding of the nature of their actions, may have diminished mental capacity (as young juveniles do) and thus be eligible for a partial excuse to criminal culpability.
Thus we claim that executive function grounds mental capacities vital to legal culpability, and that understanding how a diagnosis or disorder interacts with executive functioning is the best way to understand how it comments criminal responsibility. From this perspective, some psychopaths are fully responsible, and some aren't. The question isn't whether psychopaths are evil; it is whether they are capable of stopping themselves from commiting bad acts.
Our view is subject to many caveats, some of which I will discuss in my next post.