He had worked as many as 109 hours of overtime beyond his 350 regular monthly working hours in the months leading to his death.

Jiang's case was taken up by the Advocacy Network for Foreign Trainees and the Lawyers' Network for Foreign Trainees, which are awaiting confirmation of the decision from the Kajima Labour Standards Inspection Office.

As Japan's own population ages, its factories are turning overseas for fresh workers. The Japanese International Training Co-operation Organisation says there are about 200,000 foreign 'trainees' working in Japan at present, with more than 70 per cent of the total from the mainland. They work across 124 industrial sectors but are not allowed in the service sector.

Now, Jiang's case is about to force Japan to reform its practice of using foreign trainees as virtual slaves.

'We have not been formally told of the decision, as we still need to provide the office with some documentation about his family, but I have heard that a decision has been made, and this really would be a landmark ruling,' Lila Abiko, a lawyer representing Jiang's family, told the South China Morning Post.

The labour inspection office has submitted papers to prosecutors against the company and its owner, who has not been named, accusing him of violating the law by forcing employees to work excessive hours and failing to pay them overtime.

The lawyers' group has learned that the company kept two time cards for its staff: one that could be shown to inspectors from the Ministry of Health, Labour and Welfare, and one that recorded the employees' real working hours.

The time cards for the months immediately before Jiang's death have been destroyed, but earlier cards show that in November 2007, for example, Jiang put in 180 overtime hours, meaning that he worked more than 17 hours every day of the month. He had not taken a day off in the 19 days before he died on June 6, 2008.

Further investigations revealed that the mainland interns were paid 400 yen (HK$35.42) per hour of overtime, far below the minimum wage, and that the company had not been paying their insurance contributions and owed three employees a total of about 180,000 yen in unpaid wages.

The company's president continues to protest his innocence, telling the media Jiang had wanted to put in lots of overtime and showed no signs of ill-health at regular health checks.

But the lawyers' group says what happened to Jiang is symptomatic of the abuses that are inherent in the government-run scheme designed to provide assistance to developing countries in the form of educational opportunities. They say it has become open to abuses that make it a form of slave labour and that the victims have few rights.

The lawyers' network is representing more than a dozen trainees who have been mistreated. Wages of some of them have been withheld, and others have been forced to hand their passports over to their new employers, effectively making them illegal aliens and less likely to complain about abuses.

'In the past year, there were 27 technical interns who died in Japan, many of them from causes that can be linked to overwork,' Abiko said.

'That figure may be an improvement on the 35 deaths in 2008, but it is still far too high and completely unnecessary.'

As soon as the labour bureau officially announces its ruling, the lawyers plan to apply for Jiang's wife and young daughter to travel to Japan to begin the procedures for receiving a labour insurance payment that is likely to be about 10 million yen.

After that, they plan to sue the company, not least to send out a message to other companies that are taking advantage of foreign workers.