As mentioned previously here and here the group of journals collectively known as PLoS have published some controversial articles recently related to criminal law and science. Today, PloS Biology does it again with this article discussing the implications of modern neuroscience and the law. Time constraints prevent a detailed post today, but of particular note are the author's speculations that neuroscience findings question the existence of free will and their argument that neuroscience will revolutionize thinking about moral responsibility. These are popular claims these days, with many proponents offering colorful pictures of the brain as some sort of persuasive evidence that we're just products of the brain's biological outputs. And, of course, in some respects we are: all behavior is associated with some biological actions. Everyone has biological propensities of some sort; we do inhabit a biological body. But it's a far cry from saying that to suggesting that individuals cannot engage in free choice and rational decision making.
But that's just the beginning. The authors of the present study make several claims that simply don't deserve merit. For instance, they point to the use of fMRI as lie detectors but mostly neglect the mountain of empirical research that has demonstrated that fMRI's are not reliable and valid in measuring deception. Additionally, after discussing some findings suggesting a link between brain abnormalities and aggression, the authors next state that 25% of defendants examined for competency to stand trial are found mentally ill and cite this study (which is hardly epidemiological or representative). Of course, what the authors fail to mention is that the vast majority of incompetent defendants suffer from psychosis and not from minute defects of the frontal cortex or amygdala.
Likewise, the authors discuss the famous case of Phineas Gage who suffered a severe brain injury and was observed to have substantial changes in his mood and personality.
But cases such as Gage are exceedingly rare and the implicit assumption that what was true for Gage may be true for multitudes of defendants is simply unsupported rhetoric. Moreover, the notion that some behaviors cause criminal behavior not only mixes normative legal thought with pseudoscience but ignores a fundamental precept of science: correlation does not prove causation. For the criminal law, the issue isn't whether a defendant has a biological predisposition towards behavior X, but whether at the time of the offense the defendant's mental capacity was so impaired as to leave him incapable of knowing his behavior was wrong. Such restrictive standards hint at a collective norm which holds people accountable for their behaviors irrespective of their propensities unless there is a fundamental and overwhelming breakdown of the mind. Everyone comes from some biological and environmental background and we all flourish and suffer because of it. To allow simple biological abnormalities to control our criminal law would be tantamount to excusing everyone. More importantly, as much as we have learned about the brain (and we have learned a lot) the empirical literature simply cannot support the sweeping claims made about free will and intentionality that so many, albeit popular, authors make these days.