Neurolaw: The Potential and Pitfalls of a Newly Developing Field

Posted By Jey Kumarasamy

Neurolaw is an emerging field at the nexus of neuroscience and law. This blog post discusses the use of neuroscience in the legal system and its issues. The interest in neurolaw increased in the 1990s with advances in functional neuroimaging (e.g. fMRI). Functional neuroimaging measures neural activity in a specific region of the brain, which could then be used to explain one’s behaviour.

In 2000, a middle-aged male schoolteacher in Virginia was accused of collecting child pornography and trying to molest his stepdaughter. After complaining of headaches and a loss of balance, he underwent a brain scan. The MRI results revealed an egg-sized tumour pushing against the prefrontal lobe of his brain. This area of the brain controls judgment, impulse control and social behaviour. Once the tumour was removed, he stopped downloading child pornography and making unwanted sexual advances toward hospital staff. However, this lasted for only a year before he returned to his old behaviour. Another brain scan indicated that his tumour had returned. Once again, he started behaving normally after the tumour was removed. This is a rare case with a clear causal link between the neurological abnormality and criminal behaviour.

“My brain made me do it”

In Canada, there were 31 criminal cases that discussed electroencephalography (EEG) and 118 that discussed magnetic resonance imaging (MRI) between 2005 and 2010. In the US, the number of cases involving neuroscientific evidence doubled from 2006 to 2009.

In criminal law, one of the two essential elements for criminal liability is mens rea (i.e. the required mental element for the crime, often criminal intent).[1] With the development of the field of neurolaw, the defence in a criminal case can now put forward, for example, a neurological condition as an excuse from responsibility.

An early example of a criminal case in which the defence submitted neuroimaging evidence is R v Parks. The accused, Kenneth Parks, drove 23 kilometres to his in-laws’ house and attacked them with a kitchen knife and a blunt instrument, presumed to be a tire iron.[2] His mother-in-law died but his father-in-law survived. Parks then drove to a nearby police station and told the police that he thought he had killed both of them. The defence successfully argued that Parks could not be held responsible because his somnambulistic condition (i.e. sleepwalking) was legally classified as non-insane automatism. The evidence included an EEG report, which measured unusual activity in his brain. [3] The evidence satisfied the jury, and Parks was acquitted. In 1992, the Supreme Court of Canada upheld this decision.

Neuroscience also played a part in the landmark US Supreme Court case Roper v Simmons (2005) that found juvenile death penalties unconstitutional partly because of differences between juvenile and adult minds. The American Medical Association (AMA) and American Psychological Association (APA) each filed briefs citing studies that demonstrated “neurological, physiological, and psychological deficits” in the adolescent brain.

Potential applications

Although neurolaw has so far been used mostly by the defence in criminal cases, neurolaw may also be of some benefit to the prosecution. Application of neurolaw in Canada by the prosecution in criminal cases is quite possible in the future. It would also raise privacy issues, and necessarily shape privacy laws concerning an individual’s thoughts and memory. But it also highlights the pitfalls of neurolaw. For instance, a trial in India resulted in the conviction of a woman for the murder of her ex-fiancé. The decision was largely based on a brain scan using a new technology – Brain Electrical Oscillations Signature (BEOS). BEOS claims to be the next-generation lie detector. However, critics were alarmed that, at the time of the case, no peer-reviewed studies of BEOS had been published. The accused’s sentence was later suspended by the Bombay High Court, which made no mention of the BEOS evidence.

Advances in neuroscience may also have the potential to affect other aspects of the legal system. Procedures that might accurately measure one’s pain could revolutionize the way courts deal with personal injury (tort), workers’ compensation or insurance litigation. In the future, we could potentially use neuroimaging to confirm lack of bias in a prospective juror or as supporting evidence that the accused or a witness recognizes something.

Possible issues

As with any developing technology, many of the technologies commonly associated with neurolaw are not perfect and, in some instances, not reliable enough for use in court. Neurolaw usually relies on a correlation between brain activity in a specific region and a particular behaviour, but as the maxim states: correlation does not (necessarily) imply causation. In some cases, like the above-mentioned in which a man suddenly developed a sexual obsession with children, a causal link does seem evident; but such cases are the exception rather than the norm. Furthermore, brain scans are typically performed after the crime is committed. Can brain scans performed several weeks later ever accurately depict the mental state of the accused while committing the crime?

A recent study published in Science found that judges are more likely to list mental illness or psychopathy as a mitigating factor when sentencing an accused if there is evidence of a biomechanism underlying the psychopathy. The researchers presented the same psychiatric testimony as part of a hypothetical case to 181 trial judges, but some judges also received “expert testimony from a neurobiologist who presented an explanation of the biomechanism contributing to the development of [the] psychopathy”. The results suggested that the inclusion of biomechanical evidence led to significantly reduced sentences for the accused (from 13.93 years to 12.83 years), “and increased the proportion of judges listing mitigating factors (from 29.7 to 47.8%)”. This is an interesting result in light of the growing prevalence of neurolaw. For instance, it demonstrates the need for a discussion on the fundamental differences in a legal context, if any, in formulating the same psychopathy in physiological terms or in psychological terms.


The potential impact and promise of neuroscience in our legal system is unquestionable. Neurolaw could revolutionize the way we think of and apply the law. However, as some of the examples above illustrate, it is important that we tread with caution. The outcomes of many future cases depend on how we answer the many legal and scientific questions raised by the incorporation of neurolaw.


[1] Kent Roach, Criminal Law, 4th ed (Toronto: Irwin Law, 2009) at 9.

[2] R v Parks (1990), 73 OR (2d) 129, at paras 14-15.

[3] Ibid at 20.

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