Five years ago this week, Prime Minister Ariel Sharon was removed from office. It was a stroke that brought him down, but with the changes that would have been required by the nature and seriousness of the charges against him, he was a step away from Moshe Katsav's criminal end.

In 2004, Sharon was to have stood trial for the Greek island affair, on the recommendation of then-State Prosecutor Edna Arbel and with the support of the prosecution team and the police investigations chief, Moshe Mizrahi.

The recommendation was shredded up by then-Attorney General Menachem Mazuz, with the support of another team, not for lack of guilt but for insufficient evidence.

Mazuz's actions in closing the Sharon case and in the plea bargain in the Katsav case are similar. He deliberated mainly over whether the evidence would be enough to convict - and in fact whether the judges would think so.

In the Greek island affair, Mizrahi and the head of the national fraud squad, Miri Golan, presented telling evidence that Arbel believed would have led to a conviction. But Mazuz, who at the time also thought Aryeh Deri would not be convicted, entrenched himself in his skepticism, which from the outset was one of the reasons he was appointed.

For some reason between January and June 2007, Mazuz pulled back from almost completely accepting the recommendation of the investigation team in the Katsav case, headed by Yoav Segalovitz, for a plea bargain (including the rape charge, and excluding the charges of wiretapping and fraudulently accepting gifts ), approved by the head of the Investigation and Intelligence Branch Yohanan Danino.

Instead, he went for the watered down plea bargain. Mazuz's mistake in assuming that evidence was insufficient was revealed by Katsav, who insisted on turning down the plea bargain after it had been barely approved by the High Court of Justice - the same court that had reconciled itself to Mazuz's decision to close the Sharon case.

How did it happen that Segalovitz was right all along and Mazuz was saved from humiliation only because Katsav acted foolishly? It turns out that attorney Segalovitz, as a veteran police prosecutor and investigator, was a greater criminal expert than attorney Mazuz.

The investigation was masterful, analyzing not only what stood out clearly under the lamp, but also what was in the shadows.

For example, the investigators studied the data from Katsav's cell phone - his personal one and the one in his car - and used it to draw conclusions from the silence between calls. That was a brilliant stroke a la Sherlock Holmes in deciphering the secret of why the hounds of the Baskervilles did not bark.

This was all done under difficult conditions, in which the suspects are senior officials who enjoy immunity from arrest and search.

This immunity should be reconsidered. It was intended to prevent the government from abusing opposition lawmakers with minor issues or fabrications, or to prevent political power from changing hands due to investigations of people in office. The main goal of investigations, trials and convictions, in addition to punishment, is after all, deterrence.

Instead, a mechanism should be instituted similar to the appointment of an investigative judge in certain cases of death, such as suicides of prisoners (the case of entertainer Dudu Topaz was not the last in this series ).

The attorney general should be able to persuade the judge to lift the suspect's immunity, at least with regard to a search; the Shin Bet security service should cooperate in handing over documents, as was partially done in the Katsav case, and in having body guards testify. Politicians who are deterred by the new rules would be invited to retire and seek another line of work.

Katsav's refusal to admit of his own free will to some of the charges and receive a relatively light sentence reflects the culture of "shame" as opposed to "guilt." Sharon, if he had been pushed into such a corner by Arbel (or by the later Mazuz ), would certainly have coolly considered the deal and signed it as a painful but convenient measure.

How will another survivor of the Greek island affair act - former Prime Minister Ehud Olmert, in the cases currently before the courts and others (Holyland ) waiting their turn.