Neuroscience and the Law

Brain scans in the courtroom, fMRI lie detection, the teenage brain in Supreme Court decisions, tumours and responsibility, eyewitness memory — and the limits of using group-level brain science to judge individuals.

Neurolaw studies how neuroscience bears on legal questions about responsibility, evidence, punishment and rights.

Brain evidence and responsibility

Defence lawyers sometimes present brain scans to argue that a defendant had reduced control or understanding. A famous historical case is Charles Whitman, who killed his mother, his wife and many others at the University of Texas in 1966; his autopsy found a brain tumour near the amygdala, and he had written of strange urges — though whether the tumour caused his actions can't be known. A 2003 report described a man who developed paedophilic urges that disappeared when a large orbitofrontal tumour was removed and returned when it regrew.

Most legal scholars caution that brain differences explain behaviour only probabilistically. Many people with similar brain findings never commit crimes, and the law's test of responsibility — can the person understand and control their actions? — is not something a scan currently answers.

Lie detection

Companies have marketed fMRI-based lie detection. In United States v. Semrau (2010–2012), federal courts excluded such evidence as not meeting scientific reliability standards. Lab studies show average brain differences between lying and truth-telling in cooperative volunteers, but results in individuals are less reliable and can be defeated by countermeasures.

The adolescent brain and sentencing

In Roper v. Simmons (2005), the US Supreme Court abolished the death penalty for crimes committed under age 18. In Graham v. Florida (2010) and Miller v. Alabama (2012), it limited life-without-parole sentences for juveniles. The Court cited research — including brain science, submitted in briefs by organisations such as the American Psychological Association — showing adolescents are more impulsive, more susceptible to peer pressure and more capable of change. Debates continue about whether similar reasoning should apply to young adults up to their mid-twenties.

Memory on trial

Research on eyewitness memory and false memories has had concrete influence, prompting reforms in lineup procedures and jury instructions in some jurisdictions.

The big question

Some argue neuroscience will eventually undermine the idea of free will and retributive punishment; others argue the law's practical concept of responsibility doesn't depend on metaphysical free will. Either way, neuroscience raises questions about rehabilitation, prediction of future dangerousness, and fairness.