Immature Minds in a Maturing Society”: Roper v. Simmons at 20

Posted on Apr 30, 2025

Introduction Top

In 2005, in Roper v. Simmons, the United States Supreme Court held that the Eighth and Fourteenth Amendments for­bid impo­si­tion of the death penal­ty on offend­ers who were under the age of eigh­teen when their crimes were com­mit­ted.” The deci­sion, after the exe­cu­tion of twen­ty-two peo­ple who com­mit­ted crimes under the age of 18 dur­ing the mod­ern death penal­ty era, marked the end of the juve­nile death penal­ty in the United States. 

In Roper, Justice Anthony Kennedy drew on state trends in the treat­ment of young peo­ple, sci­en­tif­ic and med­ical stud­ies, and the peno­log­i­cal jus­ti­fi­ca­tions under­pin­ning cap­i­tal pun­ish­ment to sup­port the Court’s deci­sion that today our soci­ety views juve­niles … as cat­e­gor­i­cal­ly less cul­pa­ble” than oth­er defen­dants. In doing so, Justice Kennedy acknowl­edged the inher­ent arbi­trari­ness in select­ing an age cut­off: The qual­i­ties that dis­tin­guish juve­niles from adults do not dis­ap­pear when an indi­vid­ual turns 18,” he wrote, “[h]owever, a line must be drawn.” 

Twenty years lat­er, the sci­en­tif­ic, pub­lic pol­i­cy, legal, and com­mon-sense ratio­nale that sup­port­ed the Roper deci­sion has become stronger in almost every respect — with one excep­tion. The Roper Court said age 18 was the point where soci­ety draws the line for many pur­pos­es between child­hood and adult­hood.” Today, a grow­ing body of evi­dence now sug­gests that the line has been redrawn.

This report intro­duces new DPI analy­sis of the trends in sen­tenc­ing and exe­cu­tions of defen­dants age 18 to 20 based on twen­ty years of data, from the time of the Roper deci­sion on March 1, 2005 through the end of 2024.

Key Findings Top


  • New death sen­tences for 18- to 20-year-olds have dimin­ished both in absolute terms and as a per­cent­age of all new death sen­tences over the last twen­ty years. During the past five years, juries have sen­tenced just five such indi­vid­u­als to death. 

  • Since the Roper deci­sion, more than three-quar­ters of the death sen­tences giv­en to 18- to 20-year-olds have been imposed on peo­ple of color. 

  • Since Roper, peo­ple of col­or who are 18, 19 or 20 are twice as like­ly as white defen­dants in the same age range to be executed.

  • Studies of brain devel­op­ment and juve­nile behav­ior show that key fac­tors cit­ed by the Court in Roper (poor impulse con­trol and unnec­es­sary risk-tak­ing) are not only present in ado­les­cence, but also in 18‑, 19‑, and 20-year-olds.