State Rep. Monique Davis is among a group of Illinois legislators fighting to increase that age from 17 to 18, citing studies that show full brain development doesn't occur until individuals are in their early 20s, years after some youth have been sentenced to long and harsh adult prison stints.
In Illinois, 17-year-olds charged with felonies are viewed as adults, even though legislators consider them minors when it comes to alcohol, tobacco, voting, marriage, contractual obligations, or if they are victims of crimes.
Not every state operates that way. In fact, Illinois is one of only 12 states that tries 17-year-olds charged with felonies as adults.
Antoinette Kavanaugh, a forensic psychologist and adjunct professor at Northwestern University's law school, agrees that juvenile courts are better set up to serve young people.
Kavanaugh interviewed youth and adults during court trials in order to determine a person's state of mind before the trial or at the time of the crime. She said that the frontal lobe of the brain helps a person control impulses, think things through and understand consequences. It's like a car brake because it helps someone "slow down and allows you to think," Kavanaugh said. Youth, however, focus on the present more than adults and have trouble identifying risks, she added.
Youth also rely more heavily on the amygdala, a portion of the brain that controls aggression, anger and fear, which leads to overreaction, according to a report from the Illinois Coalition for the Fair Sentencing of Children.
Another important factor to consider is how trauma, environment and learning disabilities affect a youth's brain, Kavanaugh said. Youth in the legal system have higher rates of learning disabilities than their peers and have dealt with more traumatic experiences. "These things can further impede the normal functioning of the brain," she said. Stress and trauma in a young person's life can affect brain development, and though some youth may act mature for a period, they may still act impulsively.
In addition to lacking fully developed brains, teens seek sensation and are highly influenced by their peers. These factors "make kids on average uniquely different than adults," Kavanaugh said.
The National Institute of Mental Health conducted much of the available research that experts are now using to advocate for changes to outdated juvenile justice systems throughout the country.
Many of the nation's stricter juvenile sentencing laws were passed years ago, in the 1990s, before research showed that teenage brains were not fully developed. Illinois' legislators passed 15 laws in the '90s that made it easier to adjudicate youth cases in adult courts.
But it's hard to change laws back, said Elizabeth Kooy, research and policy advocate of the Juvenile Justice Initiative, because politicians don't want to appear soft on crime.
Kooy said many people in the legal system–"including prosecutors and judges–"do not understand the psychological reasons youth are different than adults. "The system is just not set up for them to look at it that way, to look at these kids as kids," she said.
National courts are starting to recognize the mental differences between adolescents and adults. In 2004, the U.S. Supreme Court banned the death penalty for offenders who were under the age of 18 when they committed crimes. The court likened its decision to a ban against executing mentally ill offenders and cited evidence that teenage brains are not fully developed. And in May, the Supreme Court ruled against life sentences without parole for juveniles in cases where no one was killed.
"We hope that laws and legislation will be changed to [ensure public safety and] reflect the differences between adolescents and adults that we now know of," Kavanaugh said.
Davis hopes that if the laws are changed, 17-year-olds can take advantage of the resources not currently available to them. Adult courts don't provide youth with the resources they need to grow and develop, while juvenile court programs focus on rehabbing young people, at times giving them access to education and therapy.
Studies show that recidivism rates are also much higher for youth who go through adult courts than for those who make their way through the juvenile justice system.
"It is just so important that we realize the talents of young people are being lost," Davis said. "These are the people we expect to become our physicians."