Though the main headline for Tuesday was that former prime minister Ehud Olmert will be going to prison, the shocker in his case is that his jail time was reduced from six years to 18 months.Upon hearing such a large reduction, many observers might have assumed it was due to the Supreme Court’s deference to Olmert’s service to the country as prime minister.He certainly got that in July 2012, when the Jerusalem District Court gave him no jail time for his Investment Affair conviction for breaking conflict of interest principles, explicitly citing his contributions to the state as part of the reason. But Tuesday that played no part in the decision.In fact, most of the five justices involved in the decision either did not make much of his being prime minister, or like Justice Salim Joubran, they held it against him as setting a poor example by being a prime minister and mayor who took bribes.So why was his prison sentence cut by 75 percent? The Supreme Court, by a 4-1 vote (Joubran being the one dissenter) actually threw out the largest conviction against him, accounting for 90% of the funds he was convicted of receiving as bribes (and leaving him acquitted of 96% of the bribery allegations he faced at the start of the case.) Instead, his conviction was upheld of accepting NIS 60,000 in bribes out of the original conviction for NIS 560,000.Four of the five justices tore apart the ruling by Tel Aviv District Court Judge David Rozen. Rozen had said the state’s main witness, Shmuel Duchner, who died during the trial, was not trustworthy all the time, but could be relied on where there was supporting evidence. He also said that, although Olmert did not get to cross-examine Duchner fully before Duchner died, this was inconsequential because Olmert had gotten to cross-examine Duchner on many issues.Duchner had been cross-examined on similar issues by seven other defendants and the court’s rejection of Olmert’s alibi left only Duchner’s version of events.The justices essentially tossed out Duchner’s testimony in its entirety.Justice Neal Hendel explained a variety of scenarios which could contradict Duchner’s testimony against the former prime minister, to explain that Olmert could be innocent even if Olmert’s alibi was a factual mess.Hendel and the other justices also seemed unimpressed with the carefully built external evidence of the prosecution, showing that Olmert would try to help his younger brother, Yossi, and that Duchner would give a bribe only if he got credit from Ehud.For example, Ehud Olmert had asked others, like American businessman Morris Talansky, to give money to Yossi.Also, there was a mountain of evidence of Ehud honoring Duchner at various events in ways which seemed hard to explain without a concrete reason, like Duchner’s story of paying bribes to Yossi at Ehud’s request.Hendel answered each issue, noting, for example, that Talansky giving Yossi funds in 2004 at Ehud’s request cannot prove retroactively what Duchner did in 2002. But there was also evidence that Duchner gave Yossi funds in 1996, importantly before 2002.The bottom line in the long-term impact of Olmert’s partial acquittal, despite how committed the Supreme Court is to upholding a high standard for proving criminal charges, is that it ironically just made it harder to obtain convictions of public figures involved in bribery.Why? It is always extremely hard to prove fraud cases, because the prosecution needs to show intent by circumstantial evidence.A bribe recipient is seldom caught holding a check as a murderer might be caught with the murder weapon.This is doubly true with public figures who, if involved in fraud, like to have aides move the funds for them.While Olmert will go to jail because of the direct testimony against him by Shula Zaken on the separate NIS 60,000 bribery charge, where he was less careful to distance himself, the next public figure considering bribery and reviewing this case to finetune his tactics for covering his tracks may not.