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

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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.

• 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.