The wife of one of the protagonists in the Rosenberg atom spy secrets case which gripped the world in the early 1950s, Ruth Greenglass gave the crucial evidence that sent her sister-in- law, Ethel Rosenberg, to her death. Her recollection as to exactly who, in 1945, had typed up secret information on the US atomic bomb project to be passed by her husband, David, to the communist Julius Rosenberg (and thence into Soviet hands) was to prove vital in the question of who, of the other participants in this espionage drama, would accompany Julius to the electric chair in 1953.

Greenglass and her husband were pivotal figures in the espionage case. David Greenglass had worked as a technician on the Manhattan (atom bomb) Project and became the conduit for the passing of its secrets to the Soviet Union.

Of the guilt of Julius there was no doubt. The second question before the court at the trial which began in New York in March 1951, was: who had typed up the notes at Greenglass’s dictation for them to be handed on to Rosenberg? The prosecution’s case against Ethel Rosenberg, who had been repeatedly interviewed, was a flimsy one. It seemed on the face of it far more likely that Greenglass, who had already confessed to spying and agreed to testify against the Rosenbergs, would have employed his wife for the task. Indeed, he had consistently asserted his sister’s innocence under questioning.

But in February 1951, with the scheduled start of the trial less than a month away, prosecutors interviewed Mrs Greenglass again, reminding her that her husband had yet to be sentenced. At that point she remembered that in the autumn of 1945 it had been Ethel Rosenberg who had typed the notes in a Manhattan apartment. Later confronted with his wife’s account, Greenglass agreed that she had a very good memory and that her version of events that had taken place almost six years before was almost certainly the right one. The admission was to send his sister to the electric chair along with her husband.

The trigger for these events in America had been the unmasking, trial and conviction in Britain of the German-born British physicist Klaus Fuchs, who had been sentenced in 1950 to 14 years in jail for passing nuclear secrets to the Soviet Union. It was evident that he had not worked alone, and in the US suspicion fell on the communist Julius Rosenberg.

Though he was not himself au fait with nuclear technology, his wife’s brother, David Greenglass, had worked, albeit in a lowly enough role as a US Army sergeant and machinist, on the Manhattan Project at Los Alamos in New Mexico. It was enough to give him access to the valuable information which he passed to Rosenberg.

When implicated himself, Greenglass agreed first to turn state’s evidence in the hope of clemency, and then to agree with his wife’s version of who had actually typed up the handwritten information he had supplied on a Remington typewriter in the Rosenbergs’ apartment on the Lower East Side, so that the Russians should receive it in an intelligible form.

Called to the stand after her husband, Ruth Greenglass corroborated his testimony.

It was enough. Julius and Ethel Rosenberg were found guilty of conspiracy to commit espionage and on June 19, 1953, both went their deaths in the electric chair at Sing Sing.

Records differ on the precise date of Ruth Greenglass’s birth, but she was born Ruth Leah Printz in New York in 1924. She grew up on the Lower East Side of Manhattan where she and Greenglass became childhood sweethearts. After leaving school she wanted to have a college education but her mother insisted that she become a typist. She married Greenglass in 1942, and both became members of the Young Communist League. After the trial verdict she lost her job as a typist to a local Republican politician. In return for her co-operation with the authorities she escaped indictment. Her husband, who received a 15-year sentence was released after serving ten years.

The veracity of Ruth Greenglass’s testimony has since been called into question, notably by a New York Times reporter, Sam Roberts, who in the 1990s conducted numerous interviews with Greenglass for his book The Brother: The Untold Story of the Rosenberg Case, which appeared in 2003.

Greenglass acknowledged to Roberts that he was no longer sure of the truth of what he had said on the witness stand: “I frankly think that my wife did the typing, but I don’t remember. You know, I seldom use the word ‘sister’ any more. I’ve just wiped it out of my mind.”

The KGB officer Alexander Feklisov (obituary November 1, 2007), who had played an important role in running Julius Rosenberg in New York, was also on record as saying that

Ethel was an innocent victim of circumstances.

After the trial Ruth Greenglass lived in New York under an alias to protect her identity. She died in April, but news of her death was revealed in court papers only on June 23 when the federal Government agreed, in response by a suit from historians, to release secret grand jury testimony.

Her husband survives her.

Ruth Greenglass, witness in the Rosenberg atom secrets espionage case, was born on either April 30 or May 1, 1924. She died on April 7, 2008, aged 83