He looked Hermann Goering and Rudolf Hess in the eyes and saw them plead "not guilty", without so much as blinking.
And three-quarters of a century on, Frenchman Yves Beigbeder, 96, one of the last surviving witnesses to the 1945-1946 Nuremberg trials of the Nazi leadership after World War II, believes the world needs international justice more than ever.
Adolf Hitler's number two Goering and ex-deputy leader Hess were among a host of top Nazis convicted by the court, with the former committing suicide before he was due to be hanged and the latter dying in jail in 1987.
Beigbeder was a nephew of French judge Henri Donnedieu de Vabres and his uncle had asked him to work as an assistant to the court in the ravaged German city that was once a symbol of the Third Reich's power.
Arriving in Nuremberg, Beigbeder, then 20, was struck by the omnipresence of Americans who were in control the city and had brought in their own culture, including hamburgers and fizzy drinks.
He worked for six months as an assistant, putting together summaries for the judge.
"I received every day the verbatim of the debates, I made summaries of 2-3 pages, dictated them to secretaries." And sometimes attended the hearings themselves.
As well as Hess and Goering, those standing just metres (yards) away from him included former Nazi security chief Ernst Kaltenbrunner, armed forces chief General Wilhelm Keitel and Hitler Youth leader Baldur von Schirach.
- 'Excruciating' -
"It was impressive, especially the contrast with the glorifying of the Nazi party and Hitler's big rallies. Here they were in long jackets, without medals and depressed-looking," he told AFP in an interview at his home in the foothills of the Pyrenees in southwest France.
There were moments when the sheer horror of what happened was made all too clear. Beigbeder remembers the testimony of Rudolf Hoess, former commander of the Auschwitz extermination camp, just after footage of corpses had been shown.
"His testimony was excruciating, because he described the operation in detail, without emotion, calmly, as if he was talking about the shops or something like that."
Echoing other testimony from those present, he recalls the confidence of Goering, who presented himself as the chief accused and was "very assured, a little sarcastic, even sardonic".
Looking at a photograph from the time, he said: "Here is Goering on the very left, very sure of himself. He was leading the dance of the accused."
"He could not bear to have other defendants confess or plead guilty."
But for most of the others "their defence was: 'It's not me, it's Hitler, I'm not guilty, or I didn't know'."
He also recalled lighter moments with a cosmopolitan mix of interpreters, secretaries and lawyers who sometimes even came together for dances at the Grand Hotel, one of the few Nuremberg buildings left intact.
- 'ICC having hard time' -
But it took many years for Beigbeder to appreciate fully the significance of what he had witnessed. Before the trial ended, he left on a scholarship to the United States, and then forged a career as a legal advisor in international organisations.
It was only from the 1990s as the international tribunals emerged that judged crimes committed in the wars in the former Yugoslavia, the Rwanda genocide and the Sierra Leone conflict that he understood the importance of Nuremberg as a precursor for international justice.
He wrote five books on their workings and insisted that Nuremberg set a "model" for future international justice.
"You can always criticise because it was the court of the victors. But the procedures, the rights of the defence were preserved, and the sentences were reasonable and nuanced."
He said that the battle against global criminal impunity was ongoing, even if the Hague-based International Criminal Court (ICC) so far lacks the power to impose itself.
"You don't take a Nuremberg step every day, because it is not the same circumstances. The International Criminal Court is having a hard time getting started," he said.
He expressed hope that US President-elect Joe Biden could make difference for the court, which was set up in 2002.
"It's difficult for heads of state to accept that their own citizens are accused of war crimes."
Beigbeder was one of a handful of survivors invited back to Nuremberg to mark the 70th anniversary of the trial, although the pandemic put paid to events planned for the 75th.
He said he remains convinced there is an "appetite for international justice" and optimistic about a "slow erosion of impunity, even if it takes 100 or 200 years."