TAIPEI - TAIWAN'S outgoing President Chen Shui-bian faces the threat of indictment in a corruption scandal that has already drawn in his wife when he leaves office after eight turbulent years.

Mr Chen will formally hand over the reins of office on May 20 to Mr Ma Ying-jeou of the Kuomintang after Saturday's presidential election, which saw the ruling party's Frank Hsieh beaten in a landslide.

What happens to Mr Chen after May 20 remains uncertain.

His wife Wu Shu-chen is already on trial on corruption and document forgery charges, but Mr Chen enjoys presidential immunity - until he leaves office.

Mr Chen's troubles began earlier in 2006 when his son-in-law Chao Chien-ming was arrested for alleged insider trading on the stock market. Chao was later sentenced to seven years in prison and is appealing the ruling.

Hundreds of thousands of people rallied on the street demanding Mr Chen step down, but he has insisted he and his family are innocent.

'I'm sure he is going nowhere but facing indictment after he retires,' said Mr Chang Ya-chung, political science professor of National Taiwan University. 'It will pose a grave challenge to him.'

Mr Chang said such an indictment 'would mark a step forward for Taiwan on the road of democracy'.

'In a mature democracy, any people breaking the law should stand trial regardless of their social status,' he said.

'Chen should go through the due legal process, and if the courts eventually find he is innocent, then he should be cleared of the charges.'

But analysts do not expect the 57-year-old former human rights lawyer, who has made several comebacks during his political life, to give up easily.

Mr Chao Chien-ming, a political analyst at National Chengchi University in Taipei who shares the same name as Mr Chen's son-in-law, said he expected Mr Chen to go radical in pushing for the island's independence.

'He will take over the turf left by his predecessor Lee Teng-hui,' Mr Chao said, referring to Taiwan's first democratically elected president. 'Chen is expected to become the new figurehead of the independence fundamentalists.' Mr Lee was succeeded by Mr Chen in 2000 and has also campaigned for the self-ruled island's independence.

'He will not retire from his political life. Unlike Lee, he is young, has ambition and the support of a party faction,' agreed analyst Andrew Yang of National Sun Yat-sen University, in the southern city of Kaohsiung.

Mr Chen was born in October 1950 to a poor farming family in southern Tainan county - humble upbringings he would later play up as part of his quest to safeguard what he called a 'native Taiwanese' government separate from China.

For a long time that won him mileage over the nationalist Kuomintang (KMT), whose leadership is largely made up of politicians with roots on the mainland.

His political capital ran out in January when the Democratic Progressive Party he then led suffered its worst ever defeat.

Mr Chen studied law at National Taiwan University, eventually becoming editor of the school's law review.

He first came into the spotlight when he represented dissident leaders who were charged with sedition in 1979, after an unauthorised protest against the KMT's authoritarian rule turned into a riot.

His career as a Taipei city councillor and lawmaker in the 1980s and 1990s was interrupted by an eight-month jail term in 1985 for accusing a professor of perjury.

Mr Chen was later elected Taipei mayor in 1994. During the 2000 presidential race, he proved adept at rallying popular support and securing the youth and blue-collar vote.

In 2000 he became the island's youngest president and the first opposition leader to take the post, ending the Kuomintang's 51-year grip on power.

Mr Chen was re-elected by a narrow margin in 2004 to a second and final term.