“Excessive bail shall not be required, nor excessive fines imposed, nor cruel and unusual punishments inflicted,” is the wording of the Eighth Amendment to the Constitution. In a 1989 case, Stanford v. Kentucky, the U.S. Supreme Court ruled, five to four, that the death penalty for 16- or 17-year-olds is not cruel and unusual punishment. Yesterday, in the case of Roper v. Simmons, the court ruled five to four that the death penalty for 16- or 17-year-olds is cruel and unusual punishment. The court majority cited “evolving standards of decency.”

The main one whose standards of decency seem to have evolved is Justice Kennedy. He sided with the majority in both 1989 and in yesterday’s opinion, which he wrote. His opinion in yesterday’s case relied heavily on what he termed “the laws of other countries” and “international authorities.” That is a perilous path, for, as Justice Scalia pointed out in his dissent, most of those other countries also don’t apply the exclusionary rule barring illegally obtained evidence, and most of them don’t have as full rights to abortion as America does. The justices seem only to use international standards when it fits their purposes.

The same selective use of evidence applies to social science research, as the Great Scalia writes. He notes that the American Psychological Association, “which claims in this case that scientific evidence shows persons under 18 lack the ability to take moral responsibility for their decisions, has previously taken precisely the opposite position.” In its brief in the 1990 case Hodgson v. Minnesota, the American Psychological Association found what it called a “rich body of research” showing, as Justice Scalia puts it, “that juveniles are mature enough to decide whether to obtain an abortion without parental involvement.”

The Supreme Court majority yesterday substituted its own judgment for that of the state legislators or voters in referenda in the 20 states, including Florida, Virginia, Texas, and Pennsylvania, who have allowed the death penalty to be applied to those aged 16 or 17. Rather than allow the state legislators and voters and jurors to weigh the social science and the international standards, the justices made the decision themselves.

Because the majority of the court cited evolving standards of decency, it seems reasonable to ask about the standards of decency of those who commit the crimes at issue in these cases. Christopher Simmons of Missouri was 17 when he, in Justice Kennedy’s account, planned a murder with his friends “in chilling, callous terms,” assuring them “they could ‘get away with it’ because they were minors.”

As Justice Kennedy’s majority opinion tells it, “Using duct tape to cover her eyes and mouth and bind her hands, the two perpetrators put Mrs. Crook in her minivan and drove to a state park. They reinforced the bindings, covered her head with a towel, and walked her to a railroad trestle spanning the Meramec River. There they tied her hands and feet together with electrical wire, wrapped her whole face in duct tape and threw her from the bridge, drowning her in the waters below.” The next day Simmons, according to the opinion, bragged about the killing, “telling friends he had killed a woman ‘because the bitch seen my face.'”

Justice Scalia’s dissent tells of another case, in Alabama, where “two 17-year-olds, one 16-year-old, and one 19-year-old picked up a female hitchhiker, threw bottles at her, and kicked and stomped her for approximately 30 minutes until she died. They then sexually assaulted her lifeless body and, when they were finished, threw her body off a cliff. They later returned to the crime scene to mutilate her corpse.”

The Supreme Court justices had a sobering reminder this week that even federal judges live at risk of such violent crimes. A federal district court judge in Chicago, Joan Lefkow, who had held a white supremacist in contempt of court, returned home Monday night to find her husband and her 89-year-old mother dead of gunshot wounds. Is it decent for that killer, if he is a 17-year-old, to know that he is immune from our most severe sanction?

Justices on both sides of yesterday’s case cited Alexander Hamilton. Justice Scalia cited Hamilton in Federalist 78, referring to a judiciary “bound down by strict rules and precedents.” Justice Scalia says the flip-flop from Stanford to Roper makes a mockery of that. Justices Stevens and Ginsburg, for their part, concurring with Justice Kennedy’s majority decision, write that if Hamilton “were sitting with us today,” they would expect him to join Justice Kennedy’s opinion for the Court.

Well, let us hear no more from liberals – say, when abortion comes before the court — about stare decisis, the principle of respecting precedent. The Founders in their wisdom allowed the Constitution to evolve not just in the interpretation by the Supreme Court but also by amendments. And the justices could be taught something about evolving standards of decency were the states to set out to amend the Eighth with one additional sentence: “The death penalty is not to be interpreted under the wording of this amendment as a cruel or unusual punishment solely by virtue of the fact that a state or a jury has decided to apply it to a person who committed a crime at age 17.”