Saturday, May 12, 2007

Law, Responsibility, and the Brain

Didn't get to post as much on this PLoS Biology article on Monday as I should have, just mentioning how valuable it was as an intro and overview to what we talk about here as the future conjunction of neurobiology and corrections sentencing. You really do need to read the whole thing, but here are a couple of whistle-whetters to make my point:

. . . the exciting discoveries of neuroscience resonate far beyond mere philosophical banter and may have important implications for the way government institutions, including education and legal systems, operate. For example, to the extent that legal systems attempt both to move behaviour in socially desirable directions and also to adjudicate transgressions fairly, the legal system's effectiveness can be improved by deepening our understandings about why people behave as they do and both how and why people respond to various changes in legal incentives. Specifically, neuroscience may have important implications for both how we understand the multiple influences on violent behaviour and how the legal system may better engage with violent criminals.


. . . one might expect that in humans, distinct neural topographies exist in, for example, the sexual criminal, the sadistic murderer, and the political terrorist. At first glance, such reasoning looks like phrenological folly; however, evidence does suggest that violent behaviour can be placed into two broad, yet distinct, categories: affective aggression (i.e., impulsive, autonomic arousing, and emotional) and predatory aggression (i.e., premeditated, goal-directed, and emotionless).

With this dichotomy in mind, Raine and colleagues reanalyzed positron emission tomography data to tease apart functional differences between premeditated psychopaths and impulsive affective murderers. Compared to controls, the impulsive murderers had reduced activation in the bilateral PFC, while activity in the limbic structures was enhanced. Conversely, the predatory psychopaths had relatively normal prefrontal functioning, but increased right subcortical activity, which included the amygdala and hippocampus. These results suggest that predatory psychopaths are able to regulate their impulses, in contrast to impulsive murderers, who lack the prefrontal “inhibitory” machinery that stop them from committing violent transgressions. Although more work is necessary, these studies strongly suggest that some kinds of criminal behaviour are associated with dysfunction of different regions of the brain.


Discussing the possibility of meaningful links between some antisocial and violent behaviour and various brain disorders can, however, enrage retributivists, who point out that moral responsibility lies in the social rules by which acts are judged—not in the brain itself. Nonetheless, there are many instances where brain disease can lead to antisocial behaviour, and these inevitably pose important complications for moral and legal systems that tend to divide responsibility for actions into dichotomous alternatives—guilty versus not guilty—instead of seeing responsibility as existing along a continuum. . . .

To be clear, there is at present no reason to believe that all criminal behaviours, or indeed even all violent criminal behaviours, are the result of organically dysfunctional brains. However, there is ample evidence to suggest that some kinds of dysfunction are likely to increase the probability of some kinds of behaviours that society labels as criminal. This suggests that research is urgently needed to elucidate the links between mental illness, neurological disorder, and criminal conduct. And modern and rapidly improving brain-imaging techniques may contribute significantly.


Advances in neuroscience could have several implications for the legal system. At the broadest level, these include (i) understanding how cognitive processes of key legal participants (such as judges and jurors) influence trial outcomes, (ii) discovering whether various assumptions underlying the evidentiary rules (such as one suggesting that “excited utterances” are less likely than average to be falsehoods) have any basis in fact, (iii) learning more about how people determine “just” punishments, (iv) anticipating how jurors may over-react to certain kinds of character evidence, (v) determining the extent of injuries from accidents, (vi) improving our abilities to detect mental biases and prejudices that may affect the proper function of legal fact-finding and decision-making, and (vii) learning more about the limits of witness memories. Yet even against this broad background, few implications for the legal system are more important than trying to gain a better understanding of important influences on criminal behaviour.

However, that very significance brings its own important challenges. On one hand, a better understanding may lead to more effective deterrence, to more effective treatment, and to more just and morally sound sentencing. On the other hand, determining criminal responsibility is a normative legal conclusion, not an empirical factual one, made in the context of a variety of often conflicting aspirations. Therefore, even the best neuroscientific study can only afford factual evidence to be weighed alongside other behavioural evidence and normative considerations, rather than actually resolve the legal question as to which the factual evidence is relevant.


. . .correlations between brain function and criminal behaviour are imperfect, calling into question both the diagnostic and predictive validity of brain-imaging evidence. That is, brain defects are not observed in all violent criminals, and conversely, not all people with PFC damage exhibit anti-social behaviour. For example, one longitudinal case study showed PFC damage to result in personality changes, but without signs of anti-social behaviour. Some studies have shown how prefrontal damage can even decrease anti-social behaviour. Differences in the PFC may also be caused by other variables, including levels of education and alcoholism. A similar pattern emerges for the amygdala, where damage can result in increased or decreased aggression. Moreover, in court proceedings, many experts have argued against the use of ambitious speculations concerning the brain (e.g., State of Tennessee v. Paul Dennis Reid Jr., 2002, No. 38887), particularly where the link between the criminal act and the neurological damage is based solely on brain-imaging data.


. . . brain images are not only powerful, they can potentially be too powerful—an effect we have referred to as the “Christmas tree phenomenon”. For example, in much the same way that a prosecutor may sway jurors with sympathetic pictures of the innocent victim, the defence may show brightly coloured images of the perpetrator's allegedly dysfunctional brain. The vividness and technological sophistication of the images may be over-weighted by the jurors, which can warp justice just as surely as can under-weighting of relevant evidence. Brain imaging can be admissible in courts of different jurisdictions (e.g., under the Federal Rules of Evidence in the United States). However, given the increasing public interest in brain imaging and the misinterpretations of what brain imaging is and can do, it is crucial for proper legal decision-making that judges and jurors understand the limitations of brain imaging.

Lots more good stuff on questions that will arise as the connections develop, on brain imaging, on free will and culpability, and other complete seminar topics. Go read. I promise you your thoughts will be aggravated at you for provoking them.

No comments: