Mr Ferencz was an inexperienced 27-year-old when he became chief prosecutor for the US in the trial of 22 officers who were part of Einsatzgruppen.
The mobile killing squads were part of Germany’s Nazi forces during the Second World War and the officers were charged in 1947 with murdering more than one million Jews, gypsies and other minorities in eastern Europe.
In his opening statement, Mr Ferencz said: “It is with sorrow and with hope that we here disclose the deliberate slaughter of more than a million innocent and defenceless men, women, and children.
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