In banning capital punishment for juvenile offenders last week, the Supreme Court once again demonstrated its pivotal role in domestic and, indeed, world affairs.
The 5 to 4 ruling swept aside laws in 20 states that permitted juries to sentence 16- or 17-year-old murderers to death, thus ending the United States' status as the last country on Earth that sanctioned the execution of those who commit crimes when they are younger than 18.
And, to a large extent, this result was due to a remarkable evolution by a single justice: Anthony M. Kennedy.
It is sometimes said that justices "grow in office," producing opinions and casting votes on the court that confound the expectations of those who appointed them. Kennedy, 68, a 1988 appointee of President Ronald Reagan, has shown his unpredictability in the past. He changed his mind in the middle of a crucial 1992 case, casting a fifth vote to uphold Roe v. Wade; he disappointed conservatives again with a landmark pro-gay-rights opinion in 2003.
Liberals gnashed their teeth when Kennedy flirted with permitting the Florida recount to continue in 2000 -- before casting a fifth vote to shut it down and propel George W. Bush into the White House.
But it is not often that a member of the court reconsiders his past views on a major issue as thoroughly as Kennedy did last week, when he supplied the court's four-justice liberal bloc the fifth vote it needed to abolish the death penalty for juveniles.
In 1989, during his first full term, Kennedy voted with a five-justice majority to uphold the death penalty for juvenile offenders. In that case, Stanford v. Kentucky, he joined an opinion by fellow Reagan appointee Antonin Scalia.
Reaching the opposite result in last week's case, Roper v. Simmons, Kennedy, writing for the majority, argued that times have changed. The number of states that either have no capital punishment or do not allow it for offenders under 18 had reached 30 -- evidence, Kennedy wrote, of "a national consensus" against the juvenile death penalty that had emerged since Stanford.
But his opinion also repudiated the legal reasoning he embraced in Scalia's opinion 16 years ago.
For example, the 1989 opinion calculated "national consensus" differently, excluding non-death-penalty states from the count; last week, Kennedy wrote that Stanford was wrong about that.
In 1989, Scalia, with Kennedy's support, wrote there was "no relevance" to laws that set 18 or more as the legal age for adult activities such as drinking and voting -- and that it was "absurd" to consider them.
Last week, Kennedy appended to his opinion a list of state laws setting the age for voting, jury service or marriage without parental consent at 18 or above. "The age of 18 is the point where society draws the line for many purposes between childhood and adulthood," Kennedy wrote. "It is, we conclude, the age at which the line for death eligibility ought to rest."
In 1989, Kennedy agreed with Scalia in brushing aside scientific studies on the relative immaturity of adolescents. Such data could not prove capital punishment fails to deter all 16- and 17-year-olds, or that juveniles are inherently less morally blameworthy than adults; judgments about deterrence and blameworthiness should be left up to legislatures and juries, the Scalia-Kennedy opinion said.
Last week, though, Kennedy cited "scientific and sociological studies" for the proposition that "it would be misguided to equate the failings of a minor with those of an adult." The weighing of such factors could not be left up to juries, Kennedy wrote, because there is "an unacceptable likelihood" that jurors would be "overpower[ed]" by the brutal details of some teenage crimes.
