Writing in The New York Times in August, Michael and Robert Meeropol called for the “government to formally exonerate Ethel Rosenberg.” The Times tweeted: “Ethel Rosenberg’s sons call on Obama to pardon their mother.”

There is a simple reason why Ethel Rosenberg should not be pardoned: she was guilty. She did in fact conspire with her husband to spy for the Soviet Union both during and after World War II. Proponents of a pardon claim that Ethel’s trial was tainted by perjured testimony, and that the death penalty was grossly unfair—and they are correct on both counts. While these assertions cast doubt on the fairness of the trial, they do not alter the fact that she was guilty.

In order to evaluate the merits of demands to exonerate Ethel Rosenberg it is necessary to understand both that she was convicted based in part on false testimony and that there is strong evidence indicating her guilt.

The case is being revived today, more than six decades after Ethel and her husband Julius were convicted and executed, as a result of the release in July of some previously secret grand jury testimony. The testimony reinforces the idea that David Greenglass lied about his sister Ethel at the trial, falsely claiming that she had typed his notes about atomic espionage in preparation for their transmittal to a Soviet intelligence officer.

The allegation that Greenglass lied about his sister’s typing isn’t new. Ronald Radosh and Joyce Milton made the charge in their book The Rosenberg File, which was published in 1983, and Greenglass admitted in a 60 Minutes interview in 2003 that he had lied on the witness stand in an effort to deflect attention from his wife, Ruth.

If the President is going to focus his retrospectroscope on the Rosenberg case, he should widen the field of vision beyond the trial and survey all of the available evidence. If he does so, Obama would find that Ethel helped her husband run a highly successful espionage operation. Julius and his espionage ring provided the KGB with detailed specifications for an astonishing range of weapons systems, including radar, the proximity fuse, jet engines, anti-aircraft weapons, and computers. Their espionage did not stop with the end of World War II. Rosenberg and his comrades were collecting information for the USSR until June 1950, just weeks before the start of the Korean War.

Ethel was aware of—and supported—Julius’ espionage from the start. A memo filed in the KGB’s archives notes that when “Antenna,” the Soviet cover name for Julius Rosenberg, began spying, he established a small Communist Party cell that included his first two agents, Joel Barr and Nathan Sussman. The cell met in Julius and Ethel’s apartment. Ethel attended the meetings and served as an unofficial secretary. A KGB message decrypted by the U.S. Army noted that Ethel “knows about her husband’s work and the role of” Barr and Sussman.

Ruth Greenglass told both the grand jury and the court about a meeting at the Rosenberg apartment in November 1944 with Julius and Ethel. Julius revealed that David was working on the atom bomb—a startling disclosure at a time when the existence of the Manhattan Project was a highly protected secret. Even though he was working at Los Alamos, David had no idea that he was part of a crash effort to create an atomic weapon.

Julius pressed Ruth to ask David to provide classified information about the Manhattan Project, and made it clear that the information would go straight to Moscow. Ruth recalled that she initially resisted the idea, and that Ethel “said that I should at least relay the message, that she felt that David might be interested, he would want to do this.”

Unlike David in his testimony about Ethel’s typing, it is clear that Ruth told the truth about this meeting, including Ethel’s participation. Her testimony matches a detailed description of the meeting that Julius related to his KGB handler. Julius noted that Ethel had stressed “the need for the utmost care and caution in informing David of the work in which Julie was engaged and that for his own safety all other political discussion and activity on his part should be subdued. At this point we asked Ruth to repeat our instructions which she did satisfactorily.”

Ethel knew at least two KGB officers, Semyon Markovich Semyonov and Alexandr Feklisov. The KGB was extraordinarily careful to keep to an absolute minimum the number of people who could compromise its officers, so its decision to allow Ethel to meet Semenov and Feklisov reflected an extraordinary degree of trust. Ethel’s familiarity with Feklisov came into play in December 1945, when the KGB needed to discuss an urgent security threat with Julius. If the coast was clear, Ethel was instructed to go to a local store for a late-night shopping trip during which she would see, but not approach, Feklisov.

Ethel played a role in covering the Rosenberg ring’s tracks as the FBI was closing in. When David Greenglass spotted FBI surveillance in June 1950, the KGB sent a message to Julius instructing him to send Ethel to the Greenglass apartment to retrieve money Julius had given David to help him escape.

In addition to KGB cables and files, there is another, more controversial source of information about the Rosenbergs’ espionage activities. After Julius was imprisoned, the FBI recruited a fellow inmate, Eugene Tartakow, to befriend and inform on Julius. In the weeks before, and during the Rosenberg espionage trial, Tartakow informed the FBI that Julius told him Ethel had “assisted me on many of my projects,” according to an FBI file. Tartakow was vilified by supporters of the Rosenbergs who said he lied in an effort to obtain a reduced sentence, but release of decrypted cables and documents from the KBG archives confirm many of his statements and refute none.

On the first day the FBI questioned Julius, he refused to grant permission for a search of his apartment. That evening, Julius told Tartakow, Ethel took cash and a Leica camera in a brown shopping bag to the apartment of a friend for safekeeping.

Ethel clearly wasn’t a master spy, and other Americans convicted of far more serious espionage offenses have received moderate prison terms. Nor was she simply a passive observer of her husband’s espionage. Just as it was wrong to execute her, it would also be wrong to exonerate her.

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Related: Cold Case: Ethel and Julius Rosenberg