Ben was born in a small village in the Carpathian Mountains of Transylvania in Romania. When he was an infant, his family moved to the United States. Ben attended Harvard University, where he studied criminal law. Ben graduated from Harvard University Law School in 1943. He joined a US anti-aircraft artillery battalion that was training in preparation for an Allied invasion of western Europe. At the end of World War II in Europe, Ben was transferred to the war crimes investigation branch of the US Army. He was charged with gathering evidence against and apprehending alleged Nazi war criminals. He ultimately became chief US prosecutor in The Einsatzgruppen Case of the Subsequent Nuremberg Proceedings.
We didn't have a regular courtroom where you could call in a witness and, uh, examine him with a secretary present and someone else cross-examining or, uh, securing his rights. We, uh, if we were taking testimony from friendly witnesses, we'd take an affidavit from them. He'd swear to it before an officer. If it was from a hostile witness, um, we would interrogate him privately, uh, in order to, uh, see if we could ascertain the truth. And when we reached the point where we felt we had ascertained the truth, we asked him to write it out in his own hand and subscribe to it as being true, and usually brought in an officer to witness that, uh, or to, uh, take a separate deposition, uh, under more favorable circumstances from a point of view of trial. And, uh, that was the evidence that we then used.