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The brother of Ethel Rosenberg, who was a star trial witness against his sister and brother-in-law in a sensational Cold War atomic spying case, never implicated his sister in an earlier appearance before a grand jury and said that they had never discussed her role "at all," according to secret court records unsealed Wednesday.

The revelation may heighten public suspicion that Ethel Rosenberg was wrongly convicted and executed in an espionage case that captivated the country at the height of the McCarthy-era frenzy about Communist allegiances.

Rosenberg and her husband Julius were put to death in 1953 after being convicted of conspiring to pass secrets about the atomic bomb to the Soviet Union, though they maintained their innocence until the end.

Historians and lawyers who reviewed the transcript said it appears to lend support to both sides of a dueling narrative — that Ethel Rosenberg was framed in an overzealous prosecution even as her husband appears to have played a central role in a sophisticated spy ring.

"You change a black-and-white Cold War narrative — framed, or traitors — into a very nuanced, gray area," said Tom Blanton, director of the National Security Archive at George Washington University, which fought for the records.

The grand jury testimony from David Greenglass, whose damning statements at the 1951 trial helped secure the Rosenbergs' convictions, had been withheld from public view even as other crucial court records have been unsealed in the last decade. A federal judge in New York, responding to requests from a group of historians and archivists, ordered the 46-page transcript unsealed following Greenglass's death last year at age 92.

The newly unsealed transcript presents Julius Rosenberg as a critical figure in an espionage operation that involved shady operatives, code names and even a secret signal to help identify couriers for the Russians.

Greenglass told the grand jury how Julius Rosenberg pressed him for secrets and discussed with him the construction and detonation of the atomic bomb. Historians believe Ethel Rosenberg was aware of her husband's activities but that the government had insufficient evidence to convict her.

Yet unlike his trial testimony, Greenglass offered no evidence to the grand jury of Ethel Rosenberg's direct involvement in the espionage and instead said he never discussed such matters with his sister. Those statements suggest Greenglass may have perjured himself at the trial when he said she had an important role, one of her sons, Robert Meeropol, said Wednesday.

"David Greenglass emphatically states that his sister was not involved. He states it under oath," he said of the grand jury testimony.

Historians had greatly anticipated the release of the documents — the final crucial piece of evidence to be made public — in hopes of learning more how a brother came to betray his sister with trial testimony that, decades later, he suggested had been partially false and given under pressure from prosecutors.

Greenglass, who was indicted as a co-conspirator and was himself sentenced to 10 years in prison, said at trial that he had given the Rosenbergs research data that he had obtained while working as an Army machinist at the Los Alamos, New Mexico headquarters of the top-secret Manhattan Project to build the atomic bomb. In especially damaging testimony, he recalled seeing his older sister transcribing handwritten notes to give to the Soviets on a portable typewriter at the Rosenbergs' New York apartment in 1945.

But the grand jury records show no mention of the typing.

Decades after the trial, Greenglass was quoted by a New York Times journalist as having admitted to lying at trial about his sister in order to protect his wife. In a May decision that ordered the records unsealed, U.S. District Judge Alvin Hellerstein noted that Greenglass said in his new statements that it was likely his wife, Ruth Greenglass — rather than Ethel Rosenberg — who typed up the notes that were passed to the Soviets.

Testifying before the grand jury in August 1950, one year before the trial, he minimized his dealings with the sister.

Greenglass recalled at one point how Julius Rosenberg was adamant that he should continue with his Army service so he could "continue giving him information, but when asked whether his sister, Ethel, was similarly insistent, he replied, "I said before, and say it again, honestly, this is a fact: I never spoke to my sister about this at all."

In the same grand jury interview, when asked whether he and Ethel Rosenberg had ever discussed commendations or citations received by the Russians, he stated: "My sister has never spoken to me about this subject."

Given the latest disclosures, Meeropol on Wednesday called on the government to finally admit that "my mother did not conspire to commit espionage" and that his father "was not an atomic spy.'

"It is deeply troubling to see these grand jury minutes that suggest that the government actually either deliberately put on testimony it knew to be false, or at least put on testimony it had reason to doubt its accuracy (about) in a capital case like this," said attorney David Vladeck, who argued for the documents to be released.