Why did Stevenson believe that being an adolescent and childhood experiences contributed to criminal behavior?

According to Stevenson, adolescents are still developing biologically and psychosocially, meaning they weren’t as capable of impulse control. The stress of being a teen, particularly a poor teen in dysfunctional environments, compounded their likelihood to lack the maturity and judgment necessary to make reasoned decisions. Stevenson takes the case to the Supreme Court and asks that life-without-parole sentences for children be ruled unconstitutional. During his oral argument, he says that the U.S. violates international law by imposing such sentences on children.