The Link Between Brain Imbalances and Criminal Behaviour

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With a growing understanding of genetic influences on behaviour and personality, researchers suggest that neuroscience should be highly relevant in the criminal justice process.

Neuroscientist David Eagleman argues that less emphasis should be placed upon punishing offenders with brain imbalances, and that neurobiology should be used to manage criminality generally.

Justifications for Sentencing

Section 3A Crimes (Sentencing Procedure) Act 1999 sets out the purposes of sentencing, which are:

(a) to ensure that the offender is adequately punished for the offence,
(b) to prevent crime by deterring the offender and other persons from committing similar offences,
(c) to protect the community from the offender,
(d) to promote the rehabilitation of the offender,
(e) to make the offender accountable for his or her actions,
(f) to denounce the conduct of the offender,
(g) to recognise the harm done to the victim of the crime and to the community.

Mental Condition

An offender’s mental condition can, in certain circumstances, lead to a finding of reduced moral culpability, causing less emphasis to be placed on ‘general deterrence’ (ie deterring others from committing crimes) and ultimately resulting in a more lenient penalty.

The rationale for this was explained in the case of Muldrock v the Queen, where the High Court said:

“General deterrence should often be given very little weight in the case of an offender suffering from a mental disorder or abnormality because such an offender is not an appropriate medium for making an example to others.”

Indeed, reports by psychologists and psychologists are often used inside the courtroom as evidence of an offender’s mental condition or illness, and can help bring about a reduced penalty.


Neuroscience deals with the structure and function of the nervous system and brain.

American psychologists Joshua Greene and Jonathan Cohen argue that people with concentrations of brain activity which are different to the general population may be far less able to control their actions, and therefore more prone to criminality.

As punishment is founded on the notion of free will, they argue that those with genetic anomalies which reduce control should receive less punishment for their crimes than other, normal-functioning people.

Explaining Behaviour

Recent studies show that certain types of offenders have different brain structures and functioning to the general population, a phenomenon they believe might explain patterns of offending.

Studies have particularly focused on the difference between those with acute antisocial personality disorder, also known as psychopathy, and non-psychopaths. Psychopaths typically lack empathy, guilt, conscience or the ability to show remorse. As a result, psychopaths are estimated to comprise 20% of prison inmates, compared to just 1% of the general population.

Brain scans have found that psychopaths have, on average, much lower volume and activity in the brain’s frontal lobe (specifically the middle and orbital frontal gyrus), as well as the amygdala. These parts are generally associated with emotional control, influencing the production of empathy, remorse and guilt, as well as regulating our impulses and judgment.

One of the best-known examples of brain-changes influencing criminal behaviour was Charles Whitman, the 1966 University of Texas Shooter. While Whitman was previously quite unremarkable, his suicide note requested an autopsy to determine why he had begun to have “many unusual and irrational thoughts.”

The autopsy indeed revealed an extremely aggressive tumour impinging on brain tissue, which reduced the functioning of his amygdala.

Australian Case Studies

Neuroscience has certainly been used inside Australian courtrooms.

In sentencing 49-year-old Jordan Furlan in 2014 for manslaughter, Justice Croucher considered evidence of a brain injury some years before the offence. The Judge found that Furlan’s “moral culpability was reduced, but only to a moderate degree because his judgment was impaired as a result of his acquired brain injury”. Furlan received a reduced sentence of three years and six months.

Similarly, the sentence of Terry Martin in Tasmania for child sexual offences was reduced in light of evidence he had developed a compulsive form of sexuality resulting from the effects of medication for Parkinson’s disease on the dopamine system of his brain.

Neoroscience has also confirmed that the areas of children’s brains which control judgment are less developed than those of people aged in the mid-twenties onward, which supports the long-established idea that children, especially young children, should not be held criminally responsible to the same extent as adults.

Interplay Between Neuroscience and Choice

Even the staunchest proponents of the link between neuroscience and criminality concede that those with “abnormal” brains still have choices. They therefore fall short of arguing that criminal responsibility should be entirely absolved due to differences in brain functioning.

Professor Jeanette Kennett from Macquarie University believes that taking the link between neuroscience and criminality to the extreme, “would undermine the whole notion of responsibility, and undermine the attributive basis of the law.”

So although neuroscience may go some way towards explaining criminal conduct, it should not be used to excuse all responsibility.

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About Zeb Holmes

Zeb Holmes is a journalist and paralegal working on claims for institutional abuse. He has a passion for social justice and criminal law reform, and is a member of the content team at Sydney Criminal Lawyers®.

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