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A pair of psychology and legal experts discussed the role neuroscience plays in legal decisions about the death penalty at a panel hosted Thursday by the Petrie-Flom Center at Harvard Law School.

The seminar featured Harvard Psychology professor Leah H. Somerville and Stephanie Tabashneck, a fellow at the Harvard Law School’s Center for Law Brain and Behavior.

The pair discussed the neurological research the Supreme Court has relied on for years when deciding cases related to the death penalty and life without parole sentencing for young adults.

Somerville discussed the key role the prefrontal cortex plays in decision-making.

“The prefrontal cortex may be of particular interest today because it’s crucial for a number of cognitive functions, like planning, decision making, and various forms of self-control, broadly construed,” she said.

She said the brain — including the prefrontal cortex — is not done developing by the age of 18 when Americans become legal adults. Adolescents’ underdeveloped brains can lead to riskier behaviors, depending on the environment in which people grow up, Somerville said.

“Adolescents aren’t uniformly having a taste for risk in every condition, but rather, … they’re susceptible to certain kinds of environments or contexts that might drive up that tendency to engage in greater risk-taking,” Somerville said.

Results from neuroscience research were cited in several Supreme Court decisions protecting adolescent offenders from capital punishment and life sentencing. In the 2004 case Roper v. Simmons, the court held that the execution of minors under the death penalty was unconstitutional. Justices banned life imprisonment without parole for minors in the 2011 case Miller v. Alabama.

“The court articulated that the general differences between kids under 18 and adults are also present for those who are older than 18,” Tabashneck said during the panel. “And they talked about the developing brain and held that the same protections that were present for those under 18 also applied to those who are 19 and 20.”

Neuroscience research shows that brain development continues well into young adulthood, Somerville said.

“If we’re talking about the white matter that sort of feeds in and out of the prefrontal cortex, there’s research showing that it doesn’t show a plateau until somewhere in the 30s,” she said. “And so putting a specific age marker on [full neurodevelopment] is very challenging.”