WASHINGTON – Two Supreme Court justices urged Congress yesterday to provide more money to boost security at their building, saying recent attacks on federal judges underscore the need.

In a two-hour appearance before a House Appropriations panel, Justices Kennedy and Thomas also fielded questions about the court’s recent decision striking down the death penalty for juvenile killers and the health of Chief Justice Rehnquist, who has thyroid cancer.

Justice Kennedy reported Chief Justice Rehnquist was in “good spirits” and “participating actively in the work of the court.” But in response to a question, he also discussed the possibility the court will have its first vacancy in more than a decade.

“It’s a considerable amount of anxiety when there’s a vacancy: Will we get along? Will they be horrified at the work pace needed to keep up?” Justice Kennedy said. “The court can operate with less than nine, but this is worrisome because if we have 4-4 opinions it doesn’t give the system any guidance.”

Chief Justice Rehnquist, diagnosed in October, returned to the bench last month. He has not indicated whether he plans to step down when the current session ends in June.

Justices Kennedy and Thomas submitted a $60.7 million budget request to Congress, including $639,000 to create 11 new police positions for increased patrols around the court. One officer would be assigned to investigate threats made against the nine justices.

The request follows the murder in February of a federal judge’s family in Chicago, courtroom shooting deaths in Atlanta in March, and death threats against judges involved in the Theresa Schiavo feeding tube case.

The Judicial Conference of America, the federal judiciary’s policy-making board, asked Congress for $12 million to install home security systems for federal judges. But it has not been decided whether that request will cover the nine justices of the Supreme Court, which has a separate budget.

Justice Thomas told the House panel that money for the high court is needed for training in case of attempted biological and chemical attacks. He said threats are routinely made against justices’ lives, often by mail, because of the highly charged nature of their jobs.

“One thing that astounded me when I joined the court 13 years ago was how inadequate security was,” Justice Thomas said. “Passions get pretty high. I think we’ve been on borrowed time for a long time.”

At one point during the hearing, Rep. Todd Tiahrt, a Republican of Kansas, asked Justice Kennedy to explain the court’s 5-4 ruling last month overturning the juvenile death penalty partly because of international sentiment against it. Justice Kennedy wrote the opinion; Justice Thomas dissented.

“Lately we’ve had rulings that seem to go beyond the rule of law,” Mr. Tiahrt said, repeating a criticism frequently made by Justice Antonin Scalia, also a dissenter in that opinion. “We want to make sure we have separation of powers, but also make sure the Constitution is upheld.”

Justice Kennedy responded that the court has been making controversial decisions for 200 years. The Constitution’s text “must be elaborated over time,” Justice Kennedy said.