Lawyers for the Belgian criminal Kim De Gelder used images of the defendant’s brain in an attempt to convince the jury of his lack of criminal responsibility. Are brain scans the future for (neuro-) justice? The opinion of Dr. Laurent Hermoye, a specialist in brain imaging.
In 2011 an Italian court reduced the sentence of a defendant on the basis of, inter alia, MRI images of his brain, using a technique known as voxel-based morphometry (VBM), which measures the size of certain brain structures. When compared to those of a healthy control group, his scans were suggestive of a psychiatric condition underlying his crime (Feresin 2011).
For a number of years research groups have been trying to develop a lie detector based on functional MRI, to replace the polygraph. The latter, which uses physiological measurements such as heart rate, respiration, blood pressure and perspiration, has never been widely accepted in law courts because its sensitivity and specificity are questionable.
Pioneering studies in functional MRI have identified different networks in the brain which are activated by deception and by telling the truth (Mohamed et al. 2006). Two American start-up companies are even offering services in this area. However, both the sensitivity/specificity of the technique and its vulnerability to cheating (Ganis et al. 2011) are still contentious and its acceptance by the courts remains very controversial (Simpson 2008).
In a recent study published by the journal PNAS (Aharoni et al. 2013), and taken up again by the prestigious scientific journal Nature (Nuzzo 2013), Professor Kent Kiehl and his team monitored 96 prisoners over 4 years and correlated their rates of re-offending with activity in the anterior cingulate cortex (a region of the brain which is associated with, among other things, decision making) as measured shortly before their release from prison by a functional MRI paradigm in which they had to suppress impulsive reactions. They concluded that prisoners showing low activity in that area of the brain were almost 3 times as likely to re-offend as the others.
Establishing judicial truth by means of a one-hour scan would represent a revolution for the justice system. Unfortunately it is not that simple…
Each area of the brain performs multiple functions. For example, the anterior cingulate cortex, which was referred to in the Italian court and also by Professor Kiehl in his study on re-offenders, is also involved in the mediation of attention response, the control of competitive effort, motivation, error detection, working memory, the perception of pain, etc. In addition, there is no clear relationship between the activity in a region of the brain in functional MRI and the intensity of a process or an emotion.
Moreover, extrapolating conclusions reached in respect of a group to a particular individual can be problematical (Hughes 2010). While it may be true that re-offenders, when viewed as a whole, have a lower level of activity in the anterior cingulate cortex, this does not necessarily mean that an individual who exhibits this characteristic will be a re-offender.
As for psychiatric conditions, there are still no well-established indicators in brain imaging, even for conditions such as schizophrenia. Many studies show variations in groups of patients but, as discussed above, it is difficult to extrapolate these results to any particular patient.
In conclusion, it is possible that, in years to come, brain imaging techniques will become one of several elements which will be taken into account by the courts in evaluating the defendant’s degree of responsibility. Nonetheless they should be approached with caution (Oullier et al. 2012). Neuro-justice is still some way off!
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