Morton Sobell, who was convicted in the Cold War spy trial that delivered Julius and Ethel Rosenberg to their deaths, died on Dec. 26 in Manhattan. He was 101.

Mr. Sobell had served 18 years of a 30-year term in prison, asserting his innocence until 2008, when, in an interview with The New York Times, he startled his defenders by reversing himself and admitting he had been a Soviet spy. He had been convicted in 1951 with the Rosenbergs of conspiracy to commit espionage. The government portrayed Mr. Rosenberg as the mastermind of an espionage ring that provided Soviet scientists with classified conventional weapons technology and the know-how to enable them. Mrs. Rosenberg was portrayed as her husband’s partner and accomplice. Mr. Sobell was entangled in the conspiracy, although no evidence was presented that tied him to the theft of any nuclear secrets.