Gov. Deval Patrick on Wednesday signed into law a bill placing 17-year-olds accused of crimes under the jurisdiction of the state's juvenile courts.
Currently in Massachusetts, 17-year-olds are treated as adults, regardless of the circumstances or severity of the offense.
Thirty-nine other states and the federal government use 18 as the age of adult criminal jurisdiction.
In cases of violent crimes, juvenile court judges would have the discretion to impose an adult sentence. The new law also means 17-year-olds won't receive an adult criminal record.
Patrick said the new law will give young people the chance to rehabilitate their lives while holding the most violent offenders accountable.
Supporters of the change say in almost all other legal matters in Massachusetts — including voting, entering into a contract, and serving on a jury — 18 is the age of adulthood.
The Massachusetts Bar Association's chief legal counsel, Martin Healy, applauded the change.
"Seventeen-year-olds are still mentally developing, and should be treated as a juvenile under our criminal justice system," he said.
Healy said 5,000 17-year-olds are arrested each year, most for nonviolent offenses.
With reporting by The Associated Press and the WBUR Newsroom
This program aired on September 18, 2013. The audio for this program is not available.