(CNN)For the first time in nearly 70 years, the United States will execute a man for a crime he committed as a teenager.
Christopher Vialva, 40, is set to receive the death penalty on Thursday at a federal prison in Terre Haute, Indiana. He was convicted 20 years ago for the 1999 murders of two youth ministers in Fort Hood, Texas. At the time of the crime, he was 19 years old.
The crime was egregious, his attorney and other advocates agree.
But given decades of research since then on adolescent brain development, the announcement from the Justice Department raises a key question: Should a person be given the ultimate punishment for a crime they committed in their youth?
"Despite the very, very heinous nature of the crime that Christopher has been convicted for, it's my position that based on the science, his brain was not the brain of a fully fledged adult," Jason Chein, a professor of psychology at Temple University and author of a recent op-ed on Vialva's sentence, told CNN. "And that leads me to the conclusion that the punishment of taking one's life is too severe."
CNN reached out to the Department of Justice for comment, but has not heard back.
Adolescent brains are not fully mature, research shows
The Justice Department announced on July 31 that it planned to execute Vialva, along with William LeCroy, who was executed on Tuesday. It will be the seventh federal execution since the Justice Department ended a 17-year hiatus on the practice in July.
Vialva was tried for his role, along with a group of teenagers, in the 1999 carjacking and killing of Todd and Stacie Bagley in Fort Hood, Texas, according to a statement from the Justice Department.
A federal court found that Vialva shot the couple, while co-defendant Brandon Bernard, who was 18 at the time, set the car on fire to destroy evidence. Both were found guilty and sentenced to die.
The crime Vialva was convicted of was "vile" and there's no question that he should be held accountable, Chein said. But research that has emerged since his trial has shown that the brain of someone in their late teens and early twenties is not yet fully mature.
"The evidence tells us that an individual at this age has the potential for change," Chein said. "Their personality and their behaviors are not fixed the way we might think they ultimately become in a more fully matured adult."