The U.S. operates a separate juvenile justice system rooted in the idea that children are more amenable to rehabilitation and less culpable than adults. Every state allows some minors to be tried as adults, with the threshold and mechanism varying widely. Some states draw the line at 16; most use 18.
Supreme Court decisions over the past two decades have limited the harshest punishments for juveniles: capital punishment for crimes committed under 18 is unconstitutional, as are mandatory life-without-parole sentences for juveniles. Many states have passed "raise the age" laws moving 17-year-olds out of adult court.
Debates continue over how to handle serious violent offenses by minors, the conditions of juvenile detention, and whether the system should focus more on rehabilitation, accountability, or victim concerns.