An ethnic-Chinese from Africa could not be punished for overstaying her visa because the Immigration Department was aware of her status but failed to prosecute her within a three-year legal time limit, the Court of Appeal ruled yesterday. Mr Justice Thomas Gall said the Immigration Department was aware Li Li-mua, from the southern African country of Swaziland, had breached her conditions of stay after her work visa expired on October 3, 1995. Ms Li, 41, surrendered herself on October 7 last year, the court heard. The judge said the authority had three years to take action against Ms Li but failed to do so. 'In this case, the immigration authority was aware of the breach of stay immediately it occurred. From that point, which was both at the time it arose and when they were first aware of it, the authority has three years in which to bring a prosecution against the appellant. 'They were unable to do so. Their opportunity was lost.' The judge added: 'I found the magistrate was wrong in holding that point was not time-barred. The prosecution was barred from proceeding.' He allowed Ms Li's appeal against a conviction for breach of condition of stay and quashed her one-month prison sentence. Defence barrister John McLanachan argued that section 41 of the Immigration Ordinance, under which Ms Li had pleaded guilty, was 'not a continuing offence' after the first breach. Mr Justice Gall ruled that under the section it was a continuing offence, but a prosecution could not be pursued because of the three-year time limit. Outside court, Mr McLanachan said the implication of the ruling was that many overstayers in a similar situation had been wrongly jailed. Lawyer Stephen Hung, who had raised a similar argument for an overstayer in a magistrate's court in 1998, said the situation was unsatisfactory because the law was ambiguous. 'I think the authority has to make up their mind and make sure no similar cases should go before the magistracies in the future,' he said. There were 15,454 overstayers prosecuted in 1997 and 17,630 in 1998. Between January and May last year, 7,561 were prosecuted. A spokesman for the Immigration Department said it would seek further legal advice over the ruling.