Ms. Socolov refused to discuss her relationship with Mr. Gubitchev, a Russian working at the United Nations, or her legal ordeal. “The subject of her innocence or guilt was something that she would strictly not address,” Emily Socolov said.

“It’s very hair-raising to read about your mother being given a code name and moved around like a chess piece,” the daughter added. “Was she a spy? I think it’s another question that I ask: Was she part of a community that felt that they were going to bring, by their actions, an age of peace and justice and an equal share for all and the abolishing of color lines and class lines?”

“If these were things that she actually did, she was not defining them as espionage,” Ms. Socolov continued. “If you feel that what you’re doing answers to a higher ideal, it’s not treason.”

Judith Coplon was born in Brooklyn on May 17, 1921, the daughter of Samuel and Rebecca Moroh Coplon, a toy manufacturer and milliner, respectively. Her great-grandfather, a peddler who had emigrated from Prussia, was a prisoner during the Civil War at Andersonville, the infamous Confederate prison camp.

Ms. Coplon won a good-citizenship award in high school and a full scholarship to Barnard, where she majored in history and was a member of the Young Communist League. She graduated cum laude in 1943, joined the Justice Department in 1944 and, according to the government, was recruited by Soviet intelligence later that year.

In 1948, after intercepting a secret three-year-old Soviet cable, the Venona project, which monitored and decoded Soviet diplomatic communications, identified Ms. Coplon as an agent code-named Sima. She “will be able to carry out important work for us in throwing light” on United States counterintelligence, the Soviet cable said.