Japanese popular culture has few courtroom dramas. There is no Rumpole of the Tokyo Bailey, no Perry Mason in Osaka. Juninin no yasashii nihonjin, a 1991 remake of Henry Fonda's jury-room classic Twelve Angry Men, is a comedy, its title translating as "Twelve Gentle Japanese". And Shun Nakahara's film is also a fantasy; for the past 66 years, no jury has sat in Japan.

Screenwriters and defendants alike should therefore embrace the country's looming judicial reform. Currently, the pinnacle of court excitement comes when the prosecutor files a stack of summarised affidavits with the judge's clerk. This is trial by paperwork. Oral testimony is rare, and cross-examination all but unheard of. Trials not only lack drama, they give defendants little hope. Prosecutors have a better than 99.5 per cent chance of winning.

From next month, however, panels comprised of six lay jurors, called saiban-in, and three professional judges will hear serious criminal cases such as murders and rapes. In some ways, they will be even more powerful than their British counterparts, handing down sentences as well as determining guilt .

The potential for unsafe convictions under the existing system is huge. Suspects can be interrogated for 23 days, without counsel, before they're charged. Witnesses are interviewed by police and prosecutors, but not necessarily the defence. Evidence dug up by the authorities that could help the accused is often kept secret. More than 80 per cent of cases rely on a full confession.

Old-school prosecutors insist that their success rate reflects how careful they are to bring only iron-clad cases to court. "One of the concerns is that defence counsel co-operate [with prosecutors] in most cases," said Daniel Foote, professor of sociology and law at the University of Tokyo. "And there have been no claims for ineffective assistance of counsel." Indeed, Japanese has no such term.

Japan's first experiment with citizen juries came in 1928, but their impact was limited. True, the conviction rate was a more reasonable 82 per cent. But only 460 cases were contested before a jury, probably because defendants were expected to carry the extra cost. The system was dropped, "temporarily", during the Second World War. Since the list of potential jurors was almost identical to the list of men who could be conscripted, by 1943 few were available.

For liberal Britons, whose right to a jury trial was enshrined in Magna Carta, the need for 12 good men and true may seem obvious. But reform has deeply divided Japan. Some potential jurors worry that they will be asked to make life-or-death decisions in capital cases. Many more simply don't want to lose their income and freedom for no personal benefit. Critics fear that deferential laymen will convict the innocent, or that – intimidated by yakuza – they will free the guilty. "There is no denying that great submissiveness is part of the national character," Judge Tomonao Onizawa, the councillor general to the Supreme Court, told The New York Times. "But this will change gradually."

In the cavernous atrium of the Kyoto train station late last year, members of the Bar Association tried to nudge that change along by staging a not-so-traditional kabuki play about a court case. At the end, the audience were invited to vote on the defendant's guilt. Lawyers handed passers-by goodie bags labelled "Are you ready?" with Q&A booklets and a manga comic book about a murder on the golf links. Nintendo DS has just launched a new game called Guilty or Not Guilty.

The public education campaign includes three films commissioned by the Supreme Court and the Justice Ministry. Yet many people remain bemused. Unlike LA Law, there are no plot twists. The cinematic jurors end up being reassured that, "yes, the defendant was guilty", Professor Foote says.

In fact, the reforms are the result of two decades of debate within the legal community after a scandal in which four men on death row were found to be not guilty. One common thread was that their confessions, later recanted, kept shifting so that they matched new evidence found by the police. The Japan Federation of Bar Associations is calling for interrogations to be videotaped, but the Justice Ministry has conceded only that the final signing of statements should be recorded. Trying suspects before a jury of their peers is only one step towards giving defendants their day in court.