What those memories say about today’s world is no simple thing. But, after all these years, what resonates most about it is the terrifying normality of it all — Göring’s jolly charm and bluster; von Ribbentrop’s empty-headed blather; Speer’s charismatic self-promotion and salesmanship; Ohlendorf and Hoess, like two enterprising middle managers with extermination at the top of their to-do lists.

“They were without a doubt the world’s greatest living criminals, but their hands were clean, their expressions were normal, they could have been people you meet on the street,” he said. “You think what kind of a man can do this, can serve someone like Hitler, and you realize, it’s very simple. A yes man. A toady. Someone doing it for rank or uniform or money or glory.”

Mr. Sonnenfeldt, who was 21 and 22 at the time of the Nuremberg interviews, went on to live a thoroughly remarkable life. He graduated first in his class from the engineering school at Johns Hopkins, played a major role in the development of color television and the computers for NASA’s first moon shots and celebrated his 75th birthday while crossing the Atlantic by sail. He wrote a book, “Witness to Nuremberg,” and has spoken on it frequently, including many times in Germany.

But six decades on, the memories of Nuremberg are seared in his brain. There is Göring in his faded gray uniform with discolored rectangles on the collar and the lapels where his marshal’s insignia had been, bragging of his skill at submarining others in Nazi office politics.

Baffled at how the singularly unimpressive von Ribbentrop had risen so far, Mr. Sonnenfeldt once asked von Ribbentrop’s deputy, Baron Ernst von Weizsacker, how Hitler could have promoted him. “Hitler never noticed Ribbentrop’s babbling because Hitler always did all the talking,” he said.