Between the detonation of the first Soviet atomic device, in 1949, and the trial of the Rosenbergs, which began on 6 March 1951, there was a pervading fear of communist domination in the United States. This fear was escalated further by the anti-Communist witch-hunt of Senator Joseph McCarthy, which was launched in February 1950, and steadily gained momentum prior to the Rosenberg trial. By the start of the Rosenberg trial the Korean War had raged for 10 months, and the threat of spies saturated the media.
Unsurprisingly, the case enjoyed a high media profile from the outset. The case against the Rosenbergs was based principally on the testimony of Ethel’s brother, David Greenglass, who claimed that Julius had induced him to join the Communist Party. Greenglass also claimed that Rosenberg had urged his wife, Ruth, to encourage him to steal atomic bomb secrets. Greenglass implicated his sister Ethel as well, stating that she had typed documents from his notes, containing the atomic bomb information, which were then transferred up the spy chain to Moscow. Ruth Greenglass affirmed his testimony; both had agreed to co-operate with the prosecution in exchange for leniency. Nevertheless, Greenglass appeared to take particular pleasure in implicating his sister and brother-in-law.
When Julius and Ethel Rosenberg took the stand in their own defence, they did little to endear themselves to the jury, choosing to invoke the Fifth Amendment, against the advice of their defence team, rather than implicate any of their comrades. Cross examination by the prosecution seemed to focus on making them invoke this right as many times as possible, to reinforce the certainty, in the jury’s minds, that both of the Rosenbergs were hardened Communist spies.
On 29 March 1951, the jury returned a verdict of guilty on the charge of conspiracy to commit espionage and, a week later, on 5 April 1951 the judge sentenced both Julius and Ethel Rosenberg to death by electrocution.