Whitney Harris, one of the last of the prosecutors who brought high-ranking Nazi war criminals to justice at the Nuremberg trials and who, a half-century later, was a significant voice in the creation of the International Criminal Court, died on April 21 at his home in St. Louis. He was 97.

Whitney Harris, right, with Robert H. Jackson, a Supreme Court justice who was the chief prosecutor at Nuremberg.

The cause was cancer, his wife, Anna, said.

“Whitney was the last-surviving of the podium prosecutors, or in-court prosecutors, for the international tribunal,” John Q. Barrett, a law professor at St. John’s University and an expert on the Nuremberg trials, said Monday.

The International Military Tribunal, as the trials were officially known, was a joint effort by the Allied powers that formally opened in 1945, months after the end of World War II. Several prosecutors who worked behind the scenes survive, as do some who worked in the 12 subsequent war-crimes trials prosecuted solely by the United States.

Mr. Harris helped interrogate Rudolf Hoess, who had been the commandant of Auschwitz. “In those sessions, in a bloodless, unapologetic way, Hoess described the extermination system at Auschwitz,” Professor Barrett said, “and claimed that 2.5 million people had been exterminated.”

Those figures were exaggerated; the United States Holocaust Memorial Museum estimates that 1.1 million people were murdered at Auschwitz.

“There may have been a macabre twist to Hoess’s testimony,” Mr. Harris said in a speech at an international law conference in 2008. “Since he was to be labeled ‘the world’s supreme murderer’ in any case, he may have thought in his morbid mind to establish a record of mass killings never to be surpassed by any other man.”

Professor Barrett said that Mr. Harris was responsible for prosecuting Ernst Kaltenbrunner, who commanded the Reich Main Security Office, which oversaw the Gestapo and supervised the entire concentration camp system.

To support the case against Kaltenbrunner, Mr. Harris offered in evidence photographs showing him at Mauthausen, the main extermination center, alongside his security office predecessor, Heinrich Himmler, the commander of the SS, the Nazi police, The New York Times reported in 1946.

Mr. Harris was a lawyer and Navy officer when the chief prosecutor at the trials, Robert H. Jackson, an associate justice of the United States Supreme Court, recruited him as an assistant in 1945. The Office of Strategic Services, precursor to the Central Intelligence Agency, had dispatched Mr. Harris to Europe in the last years of World War II to gather evidence of Nazi atrocities.

For the 1945-46 tribunal, 24 Nazi officials were indicted; 21 were tried, one in absentia; 18 were convicted; and 3 were acquitted. On the night of Oct. 15-16, 1946, 10 of the convicted were hanged, with Mr. Harris there representing the prosecution. During the trials, he had assisted in the cross-examination of Hermann Goering, Hitler’s designated successor. Goering avoided execution by ingesting cyanide just before the hangings.

Forty-nine years after the last Nuremberg trial, Mr. Harris and two colleagues, Henry T. King Jr. and Benjamin Ferencz, joined forces to help shape the creation of the International Criminal Court. When delegates from 131 nations met in Rome to establish the court in 1998, their original draft placed war crimes, crimes against humanity and genocide under its jurisdiction. The three prosecutors traveled to Rome and lobbied the delegates to broaden the definition of war crimes to include wars of aggression, as opposed to those fought in self-defense or authorized by the United Nations.

“They used their moral authority; they were persistent, and ultimately the delegates included a reference to the crime of war of aggression in the court’s statute,” said Michael P. Scharf, the director of the International Law Center at Case Western Reserve University in Cleveland.

The I.C.C. is the first permanent international criminal court in history.

Whitney Robson Harris was born in Seattle on Aug. 12, 1912, one of two children of Olin and Lily Georgine Harris. After graduating from the University of Washington in 1933, he received his law degree from the University of California, Berkeley. In 1954-55 he was executive director of the American Bar Association.

Mr. Harris’s first wife, the former Jane Freund, died in 1999. Besides his wife, the former Anna Barwick, he is survived by a son, Eugene; three stepsons, Charles Foster Jr., Christopher Galakatos and Greg Galakatos; a stepdaughter, Theresa Galakatos; four grandchildren; and nine stepgrandchildren.

In 1948, Mr. Harris returned to the United States to teach law at Southern Methodist University in Dallas. While there he began condensing the voluminous records of Nazi atrocities he had helped recover, including Himmler’s files containing reports of the Gestapo’s systematic mass slaughters.

His book, “Tyranny on Trial: The Evidence at Nuremberg” (1954), was described by The Times as “the first complete historical and legal analysis of the Nuremburg trial” and “a book of enduring importance.”

On the 60th anniversary of the international tribunal in 2005, Mr. Harris returned to Nuremburg and walked into Courtroom 600 in the Palace of Justice, the site of the trials. Before an audience of lawyers, judges, scholars and officials, he spoke of the significance of the 1998 treaty in Rome creating the International Criminal Court.

“Although of the great powers only the United States, China and Russia remain non-signatories,” he said, “Germany, the nation whose despotic leadership brought on the Second World War, was the 23rd nation to ratify.”

He added, “No more significant approval of the principles of the Nuremberg trial and, indeed, of the principles of law and justice essential to peace on planet Earth, could ever have been made.”