Lim Kong Boon last week positively identified Mr Anwar's DNA from semen stains on a mattress belonging to Mr Anwar and the wife of his former private secretary.

He said other stains, from another male and two other women, were also found on the mattress.

"The results obtained match the control DNA used," Mr Lim testified on Monday, as Mr Anwar's sensational trial moved into its third month. "It means that the instruments used were in proper working order."

Key exhibit

The prosecution says the grey-coloured mattress came from an apartment where Mr Anwar is alleged to have taken the wife of his former secretary for sex.

The mattress was carried into court two weeks ago wrapped in brown paper.

It had 13 holes cut in it which Assistant Commissioner of Police Musa Hassan said had been where samples had been taken for comparison with samples of DNA taken from Mr Anwar.

The apartment from where the mattress was taken was the property of a company belonging to Mr Anwar's former tennis partner Solaimalai Nallakaruppan, who faces charges in a separate case of illegally possessing ammunition - a charge that carries a mandatory death sentence.

Police say they found the ammunition while investigating allegations contained in the book "Fifty Reasons Why Anwar Cannot Become Prime Minister" that Mr Nallakaruppan had arranged sexual liaisons for Mr Anwar.

Mr Anwar, who until recently was seen as the natural successor to Prime Minister Mahathir Mohamad, has pleaded not guilty to five counts each of corruption and illegal sex acts, saying he was framed by political opponents out to destroying his career.

Sodomy charges

A Malaysian doctor appearing as a prosecution witness told the court last month there was no evidence that Mr Anwar's adopted brother, Sukma Darmawan, had been sodomised.

Mr Sukma and Mr Anwar's speechwriter, Munawar Anees, were convicted in September of allowing themselves to be sodomised by the former deputy premier between March 1993 and April 1998.