THE ARREST of Carlos Ghosn, Nissan’s recently ousted chairman, on charges of financial misconduct has exposed Japan’s judicial system to global scrutiny. Mr Ghosn arrived in Tokyo last month on a routine trip as one of the world’s most feted businessmen. Now he is sleeping in a cramped, unheated cell with limited access to lawyers and family members. The prosecutors who met his private jet on November 19th at Haneda Airport can hold him for 23 days without charge. If they do not indict or release him by December 10th, they are expected to serve him with a new warrant, and hold him until the New Year.

If it was not obvious, Japanese prosecutors have extraordinary discretionary powers. The reasons are not obvious at first. Rates of crime and recidivism in the country are low, and the prison population is relatively small. This is mainly because, for social and cultural reasons, Japanese people are adept at policing themselves, and not because the police are particularly efficient. They solve fewer than 30% of crimes, and have restricted access to many of the tools considered normal in law enforcement elsewhere, thanks in part to a legacy from the 1930s and ’40s when they were considered too powerful. All the same, Japanese prosecutors derive authority from their perceived role as guardians of social order, despite the occasional high-profile miscarriage of justice.

The criminal justice system is sometimes described as “hostage-based” because it depends heavily on extracting admissions of guilt during lengthy detention periods. Suspects have no right to have a lawyer present during questioning, which has been known to go on day and night. Confessions (the “king of evidence”, as some commentators call it) underpin nearly 90% of criminal cases. The careers of prosecutors—elite bureaucrats from Japan’s best universities—rise or fall depending on their success at securing them. The conviction rate for indicted suspects is 99.8% (as opposed to 80% in the United Kingdom), partly because prosecutors avoid cases, such as rape, that they may not win. Defence lawyers go through entire careers with a handful of victories in court, possibly none. As a result, wrongful convictions are not uncommon in a country that still sends people to the gallows.

Critics have long asked for the actions of prosecutors to be brought into line with international norms. The Japan Federation of Bar Associations, a lawyers’ lobby, wants detention periods to be shortened and lawyers to have better access to clients. It says prosecutors should be forced to divulge all evidence to the defence. At present, they are under no obligation to do so, even in cases where such evidence might exonerate innocent suspects. There is no third-party body to probe miscarriages and free those wrongly convicted. The federation can claim some success in winning reform: video recording of interrogations is becoming more common, for example. But reining in prosecutors will not be easy. There is little political will to delve too deeply into a system that seems popular and efficient—unless you’re a victim of it. Despite coming under fierce pressure for their handling of the Ghosn detention, prosecutors seem little inclined to compromise. Shin Kukimoto, the deputy head of the Tokyo prosecutor’s office, says Mr Ghosn will be held for as long as it takes. “I do not criticise other countries’ systems just because they are different,” he said.