Science and the insanity defense

Writing in the Times on July 30, 2006, judge Morris Hoffman and law professor Stephen Morse defend the insanity defense. They rightly point out that the very notion of moral responsibility requires us to excuse those who don’t have sufficient capacity for what they call moral cognition. But in reaching what should be an uncontroversial conclusion, they argue that science and the law are at odds, when in fact they collaborate. They say

The rise of various materialistic and deterministic explanations of human behavior, including psychiatry, psychology, sociology and, more recently, neuroscience, has posed a particular challenge to the criminal law’s relatively simple central assumption that with few exceptions we act intentionally and can be held responsible. These schools of thought attribute people’s actions not to their own intentions, but rather to powerful and predictable forces over which they have no control. People aren’t responsible for their crimes: it’s their poverty, their addictions or, ultimately, their neurons.

This levels a false charge against science and is misleading about control. First, although materialistic and deterministic psychiatry, psychology, sociology and neuroscience deny contra-causal free will, they don’t deny human intentions or responsible agency. Rather, science shows their causes in biology and culture, and eventually might describe their neural correlates in some detail. Second, in point of fact, we aren’t in control of the powerful and predictable forces that, early in life, shape our brains, and therefore our personalities and proclivities – we aren’t self-made. Nevertheless, we form intentions, and can be held responsible for acting on those intentions, if we have normal capacities for rationality and self-control, all of which are entirely material and determined (as Morse freely admits elsewhere).

So why do Hoffman and Morse set up this straw man of science's supposed threat to responsibility, one wonders? Perhaps to carve out a special domain for the law barred from scientific inquiry - an unfortunate bit of territoriality, if true. Scientific materialism and determinism do, of course, undermine widely held supernaturalist notions of moral agency, those that ground ultimate metaphysical responsibility in contra-causal free will. So maybe Hoffman and Morse distance themselves from science in order not to offend those who suppose such ultimate responsibility is necessary for the law (which of course it isn't).

They go on to claim that “we should recognize that the criteria for responsibility — intentionality and moral capacity — are social and legal concepts, not scientific, medical or psychiatric ones.” But they immediately point out that in ascribing responsibility we recognize that “some people suffer from a mental disorder, and some do not” and of course we don’t hold responsible those with serious mental disorders. So, if psychiatric illness is real (and few would dispute this, except notoriously Thomas Szasz or, curiously, neuroscientist Michael Gazzaniga), then at least some of the criteria for responsibility are indeed medical, psychiatric and scientific.

Finally, Hoffman and Morse say that “Convicting and punishing a defendant who genuinely believed that God commanded him to kill is not unscientific, it is immoral and unjust.” But the immorality and injustice of such punishment stems directly from the fact that the defendant (Andrea Yates, for instance) suffered from a morally impairing psychosis, the diagnosis of which is a matter of science, not law. The point again is that, contrary to their op-ed thesis, the law’s definition of responsibility isn’t conceptually independent of science. Rather, neural and functional deficits in rationality and impulse control, undermining the capacity for responsibility, are precisely what medicine, psychiatry and neuroscience can help us discern. The legal test for insanity can’t be divorced from these.

Much of the injustice in the recent rollbacks of the insanity defense is due to the failure to take the science of human behavior seriously, and substitute instead the narrow, stern and retributive judgment that wrongful behavior must be punished, what ever the mental state of the accused. If they were less concerned with defending the law from science, Hoffman and Morse would discover in a materialist understanding of the mind an ally in clarifying our judgments of when a person has, or has not, the neurally instantiated cognitive capacities to be justly held responsible. We need not keep science at a distance to retain moral agency, even if we are fully material, and fully determined.