The case of "Prisoner X," an Australian-Israeli who committed suicide in prison after being secretly jailed, has a precedent in the 1980s in Marcus Klingberg, who was behind what is regarded as the most damaging Soviet spy affair in Israeli history.
Klingberg, who was deputy director of a bacteriological research centre near Tel Aviv, was arrested in 1982 for passing secrets to the then Soviet Union. The research centre's work is covered by military secrecy rules.
He was jailed for 20 years after a secret trial in 1983 and spent the first 10 years in solitary confinement.
His arrest during an operation by Israel's internal security agency Shin Bet and his sentence remained under wraps for 10 years -- only in January 1994 did an Israeli court allow publication of his case.
Klingberg, born in 1918 in Poland, was a colonel in the Soviet Red Army during World War II. He emigrated to Sweden before going to Israel in 1948.
According to the Israeli press he provided information to the KGB, the former Soviet Union's intelligence agency, for more than 20 years.
Caught because of a double agent, he was arrested in the garden of a house in Tel Aviv in view of Shin Bet's hidden cameras.
He was finally released on September 18, 1998 after serving 15 years.
Earlier appeals for early release on humanitarian grounds had been rejected: after 11 years in jail he suffered from heart disease and high blood pressure and was almost blind and moved with difficulty.
Israeli Judge Aharon Barak refused an early appeal, describing Klingberg's offence as "the most serious" in Israel's history.
He pointed to evidence from an unnamed specialist who had told the court that Klingberg's release would be dangerous, because he had in his memory "a secret of the utmost importance" which he might reveal, albeit unwittingly.
Upon her father's release his daughter Sylvia said that Klingberg was not a communist, but was grateful to the Soviet Union for having taken him in during World War II.
The other members of his family, who remained in Warsaw, were exterminated by the Nazis.