Think only gossip mags pay breathless attention to the country's hottest trendsetters? In fact, our most hallowed document, the U.S. Constitution, is at the mercy of trendiness, and some of our most conservative Supreme Court justices - Antonin Scalia and Chief Justice John Roberts, to name two - can be set all atwitter by fads.

The fad currently sweeping the country is sentencing to death rapists who victimize children.

Strict constructionism and faddishness might seem to clash. But even conservative justices recognize legal principles that recognize the inevitability of change. In death-penalty cases, the principle is "evolving standards of decency." It means that as society's view of what is acceptable changes, what is acceptable under the law can change.

People who oppose the death penalty - and I'm not one of them - have figured that America's evolving perception of what qualifies as cruel and unusual punishment would lead to abolition of the death penalty. Some polls do suggest a decline in support for capital punishment.

But while the recent debate focused on whether electrocution or lethal injection "hurt" too much, trendsetter states have changed the debate from how to who. Starting with Louisiana in 1995, six states have allowed prosecutors to seek the death penalty for people who rape children but do not kill them. The others are Texas, Georgia, Montana, Oklahoma and South Carolina.

The overwhelming legal question for Patrick Kennedy and Richard Davis is whether that is enough of a trend that Louisiana and the others can avoid the cruel-and-unusual label. Kennedy was convicted in 2003 of raping his 8-year-old stepdaughter and was sentenced to death. Davis, who was sentenced to death last year after his conviction for repeatedly raping a 5-year-old girl, is the only other person in America on Death Row for a non-homicide crime.

Since 1964, no one in America has been executed for a crime that did not involve murder. In 1977, the Supreme Court specifically disallowed the death penalty if a rapist's victim was an adult. But Louisiana legislators said - correctly, in my opinion - that raping a child under 12 is a different order of crime deserving of the death penalty.

Attorneys for Kennedy argued last week before the Supreme Court that the 44-year break in executing rapists proves that "evolving standards of decency" rule out non-homicide executions and that a few states following Louisiana's lead doesn't constitute a trend. And it never will, Chief Justice Roberts said, if the high court intervenes. "If you knock them down one by one," he pointed out, "it is kind of hard to get a trend going." Said Justice Scalia: "The trend here is clearly in the direction of more and more states permitting the capital punishment for this crime."

Is this trend simply a return to more callous views associated with the Colonial era? One count by Northern Illinois University found that, from 1800 until 1964, 924 men were executed in America for rape and 80 for attempted rape. I would argue that the new focus on rapists of children actually represents a more modern, scientifically accurate assessment of the damage such rapists inflict on the victims.

But now for the catch. As with all death-penalty issues, it's easier to make the intellectual case for execution than it is to guarantee the safeguards against executing the innocent. Too many people have been freed from Death Row because of DNA evidence to claim otherwise. Groups filing friend of the court briefs opposing the Louisiana law say that children, who would be key witnesses, often are unreliable. The threat of the death penalty might lead some rapists to kill their victims, and it might lead other victims to stay silent if their abuser is a relative.

Those are serious objections. But they are separate from the question of whether such rapists deserve the death penalty. I think the trend answering yes is likely to continue, if the Supreme Court lets it. However, a separate trend - the one in which more and more people express doubt about the ability of state and federal governments to apply the death penalty fairly and infallibly - is a good bet to become the "evolving standard of decency" that ends executions.