Criminal trials involving accused "chikan" — men who use the anonymity of crowded trains to grope women — represent the dark side of Japan's judicial system, according to their defense lawyers.

When men accused of this crime deny the charges, they are often detained for long periods and are pressured by investigators into making false confessions. Typically, police will tell them the offense "is just like speeding," lawyer Kenzo Akiyama, a former judge, told a recent public gathering on the issue in Tokyo.

The accused are usually freed if they agree to plead guilty and pay a fine.

Judges tend not to grant the defendant the benefit of the doubt, "and they do not acquit the defendant unless they are convinced of his innocence," Akiyama said.

"Close analysis of chikan cases will enable us to see how people are falsely charged, and such cases are the epitome of Japanese criminal trials," Akiyama said.

False charges of groping have drawn public attention recently following the favorable reception of the movie "Soredemo Boku wa Yattenai" ("I Just Didn't Do It"). The film by popular director Masayuki Suo depicts the struggle of a 26-year-old man falsely accused of groping who tries to prove his innocence in a system determined to find him guilty.

At the Tokyo gathering, several cases were presented in which accused gropers received not-guilty verdicts on appeal after being found guilty in initial court rulings.

In one case, a man accused of putting his left hand inside a woman's underwear and molesting her on a crowded train in Tokyo had his initial guilty verdict overturned after his lawyers argued it would have been unnatural for him to use his left hand in such a manner as he is right-handed.

They also argued he wore a large watch on his left wrist that would have hampered any attempt to molest the woman, said Kenji Kato, one of the lawyers, noting the first court rejected this argument but it was upheld on appeal.

Film director Suo, who attended the meeting, said, "I made this film as I myself was surprised at Japan's inadequate legal system and I wanted to encourage those who are victimized by it.

"It is shameful for Japan that a defendant in a groping case must go through hardships for several years in a court battle if he denies the charges," he said.