The Use of Neuroimaging Techniques in Criminal Courtrooms

By: Noshin Ullah, JD from the Lincoln Alexander School of Law at Toronto Metropolitan University

April 13, 2023

Keywords: Neuroscientific Evidence, Neuroimaging, Mental disorder, Criminal responsibility

Digitally created gavel with black background.

The heart of criminal liability often lies in the mens rea or guilty mind of an individual. What was once a black box is no longer the case – the advent of neuroimaging allows us to peer into brain activity in real time. It also allows us to view abnormalities or injuries in the brain. What then, can this tell us about a defendant’s state of mind? How should judges and juries grapple with this type of evidence? Can this type of evidence be effectively utilized for defendants who suffer from mental disorders?

Neuroimaging has come a long way since the very first ‘human circulation balance’ (a device used to measure blood flow to the brain) which was initially utilized in the 1880s. We can now visualize the brain, its anomalies, and correlate symptoms with signs. It has been especially useful in diagnosis and learning more about the functions or associations between the mind and body. Studies have delved even further into this technology and tried to re-create images (as seen by a person) based on signals received from the brain. The possibilities of peering into the human mind continue to unravel in ways that pave the path for new uses. This brings us to the question of how this technology and/or type of evidence can be used in courtrooms, more particularly in the criminal context. 

The use of neuroimaging has been more widespread in the United States, in comparison to Canada. A high-profile case that made the use of this technology well-known was the case of John Hinckley’s attempted assassination of former U.S president Ronald Reagan in 1981. The defence used a computerized axial tomography (CAT) scan to bolster their claim that Hinckley suffered from schizophrenia (more specifically, atrophy of the brain) and was insane at the time of the offence. Though the prosecution profusely protested the use of such evidence it was ultimately allowed, and the jury found Hinckley “not guilty by reason of insanity” (NGRI). 

In Canada, the equivalent of NGRI is being found “not criminally responsible” (NCR), the details of which are outlined in section 16 of the Criminal Code, 1985. Ontario’s Mental Health Act, 1990 also legislates situations where a judge may commit an individual for psychiatric evaluation/treatment if they have reason to believe that the person suffers from a mental disorder (see for instance section 21). This leads us to then explore how the use of imaging techniques fits into the scope of evidence that may be used to demonstrate the presence or such disorders. 

In his 2013 article, Professor Owen Jones outlines seven ways in which neuroscientific evidence can be used in the legal context (e.g. in the interpretation of evidence or determination of a case). Of these categories, he specifies its uses for ‘detecting’ and ‘predicting’. He suggests that neuroscientific methods can be used to find legally relevant facts in cases where a brain injury is involved or there is a question as to the reliability of memory. In conjunction with other techniques/forms of knowledge (i.e. psychology, behavioural genetics, or psychiatry), the law can make predictions about the outcome of a defendant’s treatment and their risk of recidivism. Though the legal landscape and scholarship for the use of neuroscientific evidence is still developing in the Canadian context, research has suggested that it can be useful for mitigating moral blameworthiness. Jones would classify this under the category of ‘explanation’, whereby murky facts, or the state of mind of the defendant can be illuminated by peering into brain activity. 

The most common type of neuroimaging evidence (with respect to changes in brain function) has generally been imaging that demonstrates brain damage as a result of prenatal alcohol exposure (i.e Fetal Alcohol Spectrum Disorder or FASD). This is a lifelong condition, and many individuals with FASD face systemic challenges with receiving adequate accommodations and supports. Youth with FASD are 19 times more likely to be incarcerated than peers without FASD, and as many as 30% of incarcerated adults have FASD. There is currently no process set up in Canada’s criminal justice system to screen for FASD and experts that are present during a trial (i.e. forensic psychiatrists) may not be trained to diagnose it. This results in many individuals with FASD falling through the cracks and facing the justice system without the appropriate safeguards. The importance of addressing the needs of offenders with FASD is also reflected in the Truth and Reconciliation Commission of Canada’s call to action number 34.  

Results of neuroimaging can be used to offer explanations for deviant behaviours. However, in a review of caselaw, researchers found that judges may view brain atrophy as a factor for an increased risk of recidivism or it may make them pessimistic about the effectiveness of treatment. Researchers found that judges weighed public protection more heavily than moral blameworthiness and had a greater focus on supervision, treatment, and control. Thus, using neuroimaging as evidence may not always be favourable to a defendant. 

One might be inclined to think that neuroimaging provides for a fairly reliable source of diagnosis, however not all practitioners or judges may feel the same. This warrants the consideration of mental disorders that may not demonstrate any physiological symptoms. These diagnoses can still be made by practitioners and may be considered in sentencing. Nevertheless, are juries/judges more inclined to believe or weigh a diagnosis more heavily if there is physical evidence (in the form of imaging) to corroborate it? It may also be important to consider whether all defendants should be entitled to receive a psychiatric/neurological evaluation for atrophy or mental disorders that one may not even be aware of. This would no doubt put an immense amount of pressure on the healthcare system and may therefore not be a viable option. However, it may be important to ensure that appropriate assessments are conducted should there be suspicions of specific concerns such as FASD. 

Again, the use of presenting this type of evidence can be strategic on the part of the defendant in order to mitigate responsibility for the action. But in doing so and acknowledging that there is an anomaly in the mind, a decision-maker may come to the conclusion that integration into society will never be possible and therefore an accused may be removed from the community altogether. It therefore becomes a very careful balance between pursuing justice and seeking a proportional sentence.

Nonetheless, it could open up many possibilities for those with mental disorders. Perhaps one day it may also provide a clearer picture of the guilty (or innocent) mind.