The State Attorney’s Office will not press charges over the 2010 suicide of a Mossad agent, held in solitary confinement under constant supervision, saying there is not enough evidence to establish a causal link between failures in his supervision and the prisoner’s eventual death.

The decision was made despite the findings of an investigation that determined that the Prison Service was culpable for the death of Australian-born Ben Zygier, who hanged himself with a bed sheet in the shower of his Ayalon Prison cell on December 15, 2010, while on trial for “serious charges” that reportedly stemmed from his leaking sensitive information. Additional details of the investigation were made public on Thursday after the lifting of a gag order.

A top Israeli legal analyst criticized the decision as “legally questionable and morally reprehensible.”

“We have found it would not be possible to determine with the level of certainty required for criminal proceedings that Israel Prison Service (IPS) officials and others involved in the supervision of the deceased should have foreseen his suicide,” the State Attorney’s office said in a statement. “As for the supervision defects on the day of the suicide — the investigation material will be transferred to IPS disciplinary authorities in order to determine whether supervision officials committed a disciplinary offense by their conduct regarding the deceased or their alleged deviation from procedures.”

In the investigative report, filed in December 2012, Rishon Lezion Magistrate’s Court Judge Daphne Beltman Kaduri wrote that there was evidence that failures by various elements of the IPS led to the fatality. Without identifying anyone by name, Beltman Kaduri singled out a prison officer and two prison guards whose negligence she said led to the Zygier’s death.

Zygier was kept in solitary confinement in a self-contained cell that included a toilet and shower unit. The cell was under constant supervision by a team of prison guards and included three surveillance cameras linked to a control room and a guard stationed close to the cell. A strict schedule called for visual checks on his condition every half hour with each check to be recorded in a journal.

“At the time of the incident the conditions required to fulfill the special supervision instructions for the deceased were not in place,” Beltman Kaduri wrote.

Evidence showed that the monitoring station just outside the cell was not manned, Zygier’s activities were not being recorded in a journal as required, and there was only partial supervision from the prison’s control room, the investigation established.

Among the faults that Beltman highlighted were that in the hour before his death there was no guard positioned at the cell and a journal that should have recorded Zygier’s activities was not filled in. In addition, one of the cameras in the cell was not working properly and the others were inadequate in poorly lit conditions, such as when the light in the cell was turned off.

At around 7 p.m. on December 15, 2010, Zygier, with the lights off, entered the shower and hung himself with a wet bed sheet. His body was only discovered over an hour later.

In its review of the judge’s investigative report the State Attorney’s Office argued that even checks every half hour would not have been enough to prevent a determined Zygier from taking his life. The state noted that a hanged Zygier would have died within minutes at most, far less time than the interval between periodic visual checks.

The judge’s report described an emotional meeting between Zygier and his wife on the day of his death. According to the investigation findings, Zygier asked permission to hand his wife a note and when the guard refused he tore it up angrily. When she departed, the report added, both were visibly distressed. What was said in the meeting was not disclosed.

The judge’s report determined that Zygier’s behavior, especially in light of two previous suicide attempts before his incarceration, should have warranted extra vigilance, but that the prison’s social worker did not ask for additional protective measures to be implemented.

“There is a real causal link between meticulous supervision and avoiding the late discovery of an act of suicide,” she wrote, and noted that while Zygier was determined to kill himself, the state could have prevented it. Beltman Kaduri also questioned the conditions under which the prisoner was kept and the psychological pressure it exerted on his state of mind.

“The State Attorney’s Office decision that there is no one to blame for Zygier’s death is legally questionable and morally reprehensible,” said Israel Radio legal analyst Moshe Hanegbi. “Even if he was guilty of offenses, which was never proven as the case did not reach trial stages, he didn’t deserve a death sentence.”

“In addition to the lesson learned, all aspects of the State Attorney’s decision will be studied,” the Israel Prison Service said in a statement. “The prison service would like to stress its efforts in recent years in dealing with incidents of suicide. Figures show a dramatic drop in the number of suicides.”

Zygier was in prison, among other accusations, for allegedly inadvertently leaking sensitive information that led to the arrest of informants spying on Hezbollah in Lebanon, the German paper Der Spiegel reported in March.

According to the Der Spiegel report, Zygier was arrested in Israel because he was suspected of unwittingly passing on information to a Hezbollah operative that led to the arrests in Lebanon of Siad al-Homsi and Mustafa Ali Awadeh in 2009. Both men were later sentenced to 15 years in prison for spying for Israel.

Zygier, a Jewish man from Melbourne, was trying to prove his mettle to the Israeli spy agency in an effort to regain face after failing to fulfill expectations during an operation in Europe, the German report said.

The Zygier case made international headlines in February 2013, when details of his clandestine incarceration and later suicide finally emerged, over two years after he took his own life. Before that, there were rumors in the Israel media regarding a mysterious “Prisoner X,” who was being held under absolute secrecy in the Ayalon prison.

According to reports in German and Australian newspapers, Zygier, who was apparently recruited by the Mossad spy agency in 2003, was sent to Europe in 2005 to infiltrate companies that were dealing directly with Iran. Zygier’s mission was to try to gain access to potential informants in Iran and Syria. However, after two years, during which he was employed in the accounting division of a company, Zygier was recalled to Israel without having achieved substantial results.

Zygier, disappointed, was assigned a desk job but still hoped to find his way back into the field, Der Spiegel reported. Apparently acting on his own initiative, he began trying to recruit informants in Lebanon to spy on the Hezbollah terror organization. He contacted an affiliate of the group in a Balkan state and tried to recruit him. However, the Hezbollah activist succeeding in turning the tables and duped Zygier into providing information that eventually led to the arrests of al-Homsi, Awadeh, and a string of other informants in Lebanon.

Meanwhile, after spending a year behind a desk, Zygier asked for permission to continue his academic studies in Melbourne, and in 2008 he began a graduate degree in Monash University. During the period of his studies, Zygier was apparently indiscreet about his activities with the Mossad, which eventually learned he was leaking details of his service, some of them inaccurate. Zygier was called back to Israel to face an investigation during which details of his unauthorized solo Hezbollah operation came to light. He was subsequently arrested, incarcerated under strict secrecy, and charged with what one of his lawyers said were “serious” crimes.

Israeli authorities reportedly sought a prison sentence of up to 10 years for the offenses. A plea bargain was under discussion when Zygier, who was 34 and married with two children, took his own life.

Amid myriad speculations and theories regarding aspects of the Zygier case and his alleged crimes, none of which suggested deliberate treason, Israeli authorities have remained tight-lipped over the precise details of the story.