In a law review article 15 years ago about cognitive decline on the U.S. Supreme Court, I predicted that no one would take action to mitigate the problem. Instead, another half a dozen mentally decrepit justices would join "the roster of jurists who harmed their court and hurt their own reputations by remaining on the bench too long."

Although most justices who have retired since then left with their wits (more or less) intact, I'm concerned my prediction is about to come true.

Today we have four superannuated Supreme Court justices: Stephen Breyer is 77, Anthony Kennedy will turn 80 this summer, Antonin Scalia will celebrate his 80th birthday on March 11 and Ruth Bader Ginsburg will celebrate her 83rd four days later. Both Clarence Thomas, 67, and Samuel Alito, 65, qualify for Social Security.

None of these justices has indicated that he or she will step down anytime soon, even if a like-minded politician wins the White House this year.

In the past, once-revered justices such as William O. Douglas and Hugo Black could at least count on relative privacy when they doddered into senility; the press didn't check behind certain closed doors. But with Justice Breyer showing up on TMZ, Justice Alito and Chief Justice John Roberts, 61, regularly attending public sporting events, and Justice Sonia Sotomayor, 61, getting spotted at Costco, a secret breakdown is no longer realistic.

That the two oldest justices, Ginsburg and Scalia, represent opposite poles of the ideological spectrum is a happy accident, as calls for reform must have a nonpartisan hue. Although neither has had a confirmed episode of cognitive decline, they're both putting themselves in the way of embarrassment. Ginsburg fell asleep during the State of the Union (twice), the papal address and even during an oral argument; she also speaks about pending cases, which, if not a sign that she's forgotten the rules, is an indication that she's beyond respecting them. Scalia once called himself an "old fogey" who doesn't understand the world in which he lives, and he sounds increasingly irritated in his opinions and speeches.

The problem of an aging judiciary extends beyond the Supreme Court to hundreds of elderly federal judges across the country. The average age of these jurists is now over 70, with many in their 80s and 90s. The 94 U.S. District Courts and 13 courts of appeals decide more than 98 percent of all cases with federal jurisdiction, so the continued mental acuity of these jurists should be a concern for all of us who use interstate commerce or expect due process.

Some jurisdictions have implemented programs to promote sharpness as judges age. The Ninth U.S. Circuit Court of Appeals, for instance, offers a battery of mental health assessments, hosts discussions with neurological experts and has created a hot line where staff members may report signs of decline in their colleagues. Such measures are necessary, because it's hard for friends and family members, let alone the individual in question, to know if a tendency to, say, forget one's keys is innocuous or portentous.

Unfortunately, the Ninth Circuit program and a few others exist in isolation, as there is no judiciarywide strategy to cope with cognitive decline. Roberts should use his authority as head of the federal judiciary to require his high court colleagues and others to undergo regular mental health checkups.

Further, he could recommend a judicial retirement age of 70 or 75, as is done in the rest of the Western world. He and future nominees to the bench could even pledge to serve for no more than 18 years, as has been suggested by constitutional scholars and interest groups on the left and right as a reasonable limit on judicial tenure.

Our court system and the law benefit from the wisdom of judges with many years of experience. But the federal judiciary, especially given congressional dysfunction, is simply too important to leave in the hands of old fogies.

David J. Garrow is a professor of law and history at the University of Pittsburgh School of Law. He wrote this article for the Los Angeles Times.