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U.S. District Judge Leonard B. Sand's career in the law is framed by two of the nation's most famous death penalty cases a half-century apart -- the Rosenberg spy trial and the embassy bombings case.

He began his career as law clerk for Irving R. Kaufman, the federal judge who sentenced Julius and Ethel Rosenberg to death after a New York jury convicted them of espionage.

Now, as the presiding judge in the embassy bombings case, the 75-year-old Sand is navigating a newer federal death penalty statute, one that places squarely with jurors the decision of life or death.

"He has a tremendous respect for juries," said U.S. District Judge Miriam Goldman Cedarbaum, who has known Sand for 48 years and calls him "brilliant."

The embassy bombings jury -- deliberating in the same courthouse where the Rosenberg trial was held -- is to begin hearing testimony Tuesday to determine the fate of Khalfan Khamis Mohamed, one of four defendants convicted last month of conspiracy in the 1998 bombings of two U.S. embassies in Africa.

Mohamed faces a possible death penalty for his role in the bombing of the U.S. embassy in Tanzania, which killed 11 people.

Last week, the same jurors spared the life of co-defendant Mohamed Rashed Daoud Al-'Owhali, after expressing concerns they might turn him into a martyr if they imposed the death penalty.

Sand, appointed to the federal bench by President Carter in 1978, is known for his expertise in jury instructions. He's a co-author of "Modern Federal Jury Instructions," considered required reading for lawyers and judges.

Throughout the embassy bombings trial, Sand moved the proceedings along by insisting everyone be on time and by keeping recesses brief. A trial that was expected to take up to a year seems likely to conclude in half that time.

"He keeps order in his court by the force of his dignity and personality," said Chief Judge Michael B. Mukasey of the federal court in southern New York.

Sand also has run the trial in a scholarly manner, but without the formality other judges demand. No one announces Sand's entry into the courtroom. Sometimes he leaves his black robe behind in chambers, sitting on the bench in a suit, his white beard brushing his necktie.

Sand has won praise from lawyers on both sides of the embassy bombing case.

"I've been an admirer of Judge Sand for 22 years, and while I disagree with some of his rulings, nothing he has done has made me change my opinion," said defense attorney Frederick Cohn, co-counsel for Al-'Owhali.

A graduate of Harvard Law School, Sand joined Judge Kaufman within a year of the Rosenbergs' 1951 conviction, while the exhaustive appeal in the case was still working its way up to the U.S. Supreme Court. The Rosenbergs were executed in 1953.

Since then, the death penalty statute has changed considerably, placing much more responsibility with jurors. In the Rosenbergs' trial, the law called for the judge to impose death in a capital crime unless the jury recommended mercy.

Under current law, a separate penalty hearing is held following a conviction for a capital crime. The jury's decision is binding unless a judge finds it to be tainted.

Before the embassy bombings case, Sand was best known for presiding over a Yonkers desegregation case that has spanned more than 20 years. He held the Yonkers City Council in contempt of court for resisting his housing desegregation order and imposed huge fines, nearing $1 million a day. The rulings drew protesters to his weekend home.

One of the city's lawyers in the case, Raymond P. Fitzpatrick of Birmingham, Ala., said that while Sand was "a person who clearly cares about the fairness of the judiciary," he was sometimes frustrated with the judge.

"He is very patient and very smart but in the Yonkers case at times I felt he reached conclusions too quickly," said Fitzpatrick. "I felt sometimes he already knew how he was going to rule before he heard our arguments."

Sand has been a senior judge since 1993, which gives him flexibility to turn down cases. But he doesn't hesitate taking on challenging ones, colleagues say, even a terrorist case that requires the judge to be under 24-hour security.

"He's a model of how to do the job," Mukasey said.