Harris, 97, died of cancer April 21, Anna Harris said.
After World War II, Whitney Harris helped interrogate Hitler deputy Rudolf Hess, commandant of the Auschwitz concentration camp, in the first and best-known Nuremberg trial of 22 of the most important captured Nazi leaders.
Hess was sentenced to life at Berlin's Spandau Prison, where he died in 1987.
Harris was also responsible for prosecuting Ernst Kaltenbrunner, a senior Austrian official who commanded the Reich Main Security Office, which oversaw the Gestapo and controlled the concentration camp system, St. John's University law Professor John Q. Barrett told The New York Times.
Kaltenbrunner, the highest-ranking leader of the Schutzstaffel to be prosecuted at the trial, was found guilty of war crimes and crimes against humanity and executed.
Harris also cross-examined Hermann Goering, Hitler's designated successor, who later avoided execution by ingesting cyanide just before he was to be hanged.
Harris was a lawyer and U.S. Navy officer when he was recruited in 1945 to assist chief Nuremberg prosecutor Robert H. Jackson, a U.S. Supreme Court justice.
While several prosecutors who worked the trials behind the scenes survive, Harris "was the last-surviving of the podium prosecutors, or in-court prosecutors, for the international tribunal," Barrett told the Times.
Forty-nine years after the last Nuremberg trial, Harris helped shape the creation of the International Criminal Court as a permanent tribunal to prosecute individuals for war crimes, genocide and crimes against humanity.
The court, based in The Hague, Netherlands, came into being July 1, 2002.
Harris was born in Seattle Aug. 12, 1912, and received his law degree from the University of California, Berkeley.
Besides his wife, he is survived by a son, three stepsons, a stepdaughter, four grandchildren and nine stepgrandchildren.
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