Deborah Denno was quoted in a BBC article about the role of neuroscience in the criminal justice system.
“These cases are extremely complicated. So many factors are involved,” says Deborah Denno, a professor of law at Fordham University in New York City. “The neuroscience is one of perhaps 50 variables introduced to the jury on behalf of the defendant.”
Genetic and neuroscientific evidence is typically introduced in conjunction with other factors – the abuse a defendant suffered as a child, for example, or their family history of social problems. So it’s essentially impossible to know whether it’s uniquely decisive during deliberation. “We really don’t know how people are making their decisions,” says Denno. The jurors themselves may not even know, she adds.
Real courtrooms may not be typically swayed by neuroscientific evidence, either. Paul Catley and Lisa Claydon at the UK’s Open University looked at 84 appeals against convictions heard by courts in England and Wales that featured neuroscientific evidence. They concluded that only 22 of those appeals were successful, apparently because of the neuroscientific evidence. More than twice as many of the appeals – 59 – were unsuccessful even with neuroscientific evidence.
Denno isn’t surprised by these findings. She has studied hundreds of US court cases in which neuroscientific evidence was presented in court. “I’ve never been able to conclude, even after 800 cases, that the neuroscience makes a difference,” she says.
The takeaway, he thinks, is that in certain circumstances – particularly when a defendant is likely to spend a limited time in prison and then re-enter society – genetic or neuroscientific evidence can make a big difference in court. It can lead to more severe sentences.
This idea clearly clashes with Denno’s conclusion that genetic or neuroscientific evidence doesn’t seem to make a decisive difference in court. In a 2013 paper she argued that this is because there are flaws in the study that Tabery and his colleagues performed.
For instance, Denno points out that Tabery and his colleagues chose a disorder – psychopathy – which, in their own words, is a “diagnosis with much stigma”. The judges were also specifically advised that the defendant’s condition was untreatable. This might have encouraged them to think hard about the future danger the defendant would pose to society – harder than they might have done without prompting. The researchers “loaded the dice,” says Denno.