A TOP US government codebreaker who decrypted secret Soviet communications during the cold war concluded that Ethel Rosenberg knew about her husband’s activities but “did not engage in the work herself,” according to a recently declassified memo that her sons say proves their mother was not a spy and should lead to her exoneration in the sensational 1950s atomic espionage case.

The previously unreported assessment, written days after Rosenberg’s arrest and shown to the Associated Press, adds to the questions about the criminal case against Rosenberg, who along with her husband, Julius, was put to death in 1953 after being convicted of conspiring to steal secrets about the atomic bomb for the USSR.

The couple maintained their innocence until the end, and their sons, Robert and Michael Meeropol, have worked for decades to establish that their mother was falsely implicated in spying. The brothers consider the memo a smoking gun and are urging President Joe Biden to issue a formal proclamation saying she was wrongly convicted and executed.