Should brain scans be used in the courtroom?


Roughly 5% of murder trials in the USA now involve some aspect of neuroscience in the process of coming to an overall verdict. As technology advances, we are increasingly able to provide and incorporate it into the process of meaningful societal decisions. But should brain scans be used in the courtroom?


  • The authors of the Royal Society panel, including Nicholas Mackintosh of the University of Cambridge, flag up research suggesting that the brains of psychopaths are fundamentally different to the brains of non-psychopaths. Therefore, brain scans would be crucial to determining whether or not a suspect is guilty of committing crime due to free will, as a psychopath’s disorder and subsequent altered brain structure would account for their lack of control in committing the crime. 
  • Similarly, recent research into brain development suggests that crucial brain regions such as the prefrontal cortex, which is important in decision making and impulse control, don’t actually finish maturing until the age of around 20.  
  • Brain scans provide sound methodology due to their empirical nature and objective rigour. This is seen as a desirable step forward in the courtroom as it improves accuracy of convictions by the implementation of science. The gradual removal of dependence upon subjective decisions, which are left open to the possibility of biased interpretation and subsequent inaccurate conviction, are thus seen as a good thing.


  • Lie detection research is often based on students telling lies that are unlikely to have any impact on their lives. This provides a situation that’s difficult to compare to a criminal who might be lying for his life, not to mention that of a cunningly deceptive psychopath. The lack of generalisability is arguably too great an issue to risk in serious decisions such as murder trials. Additionally, most fMRI studies are small, unreplicated and compare differences in the average brain activity of groups, rather than individuals, making it difficult to interpret for single cases. It is rarely used in diagnosis. Moreover, a recent scan, say some critics, wouldn’t necessarily indicate a criminal’s mental state when he committed his crimes, weeks, months or ever years before the scan is taken.
  • Criminals may simply learn how to trick the system. The scientific brain scans rely on physiology to generate decisions but criminals may possess biofeedback control, allowing them to manipulate their physiology. The evidence calls them innocent but they’re just playing science.
  • The easy manipulation of brain scans is confirmed by the results of one experiment, in which the success rate for distinguishing truth from lies dropped from 100% to a third when participants used countermeasures. The researchers of this study concluded that, “for the foreseeable future reliable fMRI lie detection is not a realistic prospect.”

Conclusion?:There is no harm in slowly bringing more brain scan use into the courtroom, as long as their scientific label does not cause them to be mistaken for a perfect machine of criminal judgement. They should be used with caution and not overly relied on, as a useful tool and step towards more accurate verdicts of cases involving brain injury litigation or questions of impaired ability. Their use will be a win for those who believe in biological determinism, which may fire up the old nature-nurture debate once more.