NEW YORK—Ruth Greenglass, whose testimony in the Rosenberg spy trial helped send her sister-in-law Ethel Rosenberg to the electric chair, has died. She was 84.

Her April 7 death was revealed in court documents filed in late June. She died in New York, according to Social Security records. Greenglass had been living under an alias to avoid association with the Rosenberg case.

Greenglass and her husband, David, confessed to being part of an effort to smuggle secrets to the Soviets and said Julius and Ethel Rosenberg, their relatives, recruited them. Historians continue to debate the truthfulness of their testimony.

concerning Ethel Rosenberg, whose guilt has long been questioned.

During the 1951 trial, the couple said they saw Ethel Rosenberg transcribing stolen atomic secrets on a portable typewriter in her apartment. Their account was the best piece of evidence linking Ethel Rosenberg, David’s sister, to an alleged plot to steal research data from the Manhattan Project.

By cooperating, David Greenglass, a wartime machinist in Los Alamos, N.M., who had been charged along with the Rosenbergs, was spared a possible death sentence. He served 10 years in prison. Ruth Greenglass was never charged.

Since then, decoded Soviet cables have seemed to confirm that Julius Rosenberg was a spy, but doubts have remained about Ethel’s involvement.

David Greenglass has said in recent years that he made up the account about the typewriter to protect his wife, who, he claimed, may have also improvised the tale to appease prosecutors.

Following David Greenglass’ release from prison, the couple lived in the New York area under assumed names. Her husband is still alive.