A judge has ordered the release of key grand jury evidence from 1950 that may give new impetus to suspicions that Ethel Rosenberg was unjustly convicted of espionage and put to death for conspiring to give nuclear secrets to the Soviet Union.
In his ruling, US district judge Alvin Hellerstein noted that the evidence of Rosenberg's brother David Greenglass was crucial to the case and that he claimed in interviews that prosecutors pressured him into falsely speaking against his sister.
The judge said the evidence could be unsealed now because Mr Greenglass, 92, died last year.
"The requested records are critical pieces of an important moment in our nation's history," Judge Hellerstein wrote. "The time for the public to guess what they contain should end."
The US government could still appeal against the ruling. A government spokeswoman declined to comment.
In what was called the crime of the century, Ethel Rosenberg and her husband Julius were convicted of espionage conspiracy and executed in 1953. The sentencing judge blamed their treason for the Korean War and the deaths of at least 50,000 people.
Mr Greenglass was the star government witness at the 1951 trial, saying that he had given the couple data obtained through his wartime job as an army machinist at the Los Alamos, New Mexico, headquarters of the top-secret Manhattan Project to build the atomic bomb.
He said he saw his older sister transcribing the information on a portable typewriter at the Rosenbergs' New York apartment in 1945. That evidence proved crucial in convicting Ethel, along with her husband.
Judge Hellerstein noted that Mr Greenglass told a journalist with The New York Times in 2001 that he lied at the trial about his sister to protect his wife Ruth, because it was likely that she, rather than Ethel Rosenberg, typed up notes that were passed to the Soviets.
Judge Hellerstein said Mr Greenglass claimed government lawyers were threatening to prosecute Ruth Greenglass unless he gave evidence against his sister.
Georgetown law professor David Vladeck, representing historians, archivists and writers in the litigation, said those researching the espionage case for decades would be "like a bunch of ravenous wolves" once the Greenglass transcript was released, especially since he has said in interviews that he implicated his sister in the conspiracy at trial, but not during his grand jury evidence.
"This is the last piece of major evidence that has yet to be made public," Prof Vladeck said. "I think another chapter will be written about the Rosenberg case and I think there's going to be a lot of soul searching about what happened to Ethel Rosenberg."
Prof Vladeck said historians were pretty firm in believing Julius Rosenberg fed secrets, especially after KGB documents were released. The belief is that he not only gave the Soviets nuclear technology, but also military secrets that helped them immensely in the Korean War.
Transcripts of the evidence of 43 of 46 grand jury witnesses have already been released. In 2008 Judge Hellerstein ruled that one non-profit institution, four national associations of historians and archivists and one journalist were entitled to transcripts of all witnesses who were dead, had consented to release or were presumed to be indifferent or incapacitated because they failed to object.
Three remaining witnesses - Mr Greenglass, Max Elichter and William Danziger - objected and their transcripts were not released.
Judge Hellerstein said he was ordering the release of evidence by Mr Greenglass and Mr Elichter because they had since died. The judge said Mr Danziger's evidence remained sealed because archivists had not been able to determine whether he was still alive.