SINGAPORE - The High Court on Monday (Jan 21) rejected the testimony of a witness who came forward to support the claims of a convicted sex offender who insisted that his penis was deformed at the time he was accused of sexually abusing his biological daughter.

"The various inconsistencies and shortcomings, taken together with the fact that the evidence was offered in suspicious circumstances and without any sufficient explanation, mean that the only reasonable conclusion was that the accused and the witness colluded to introduce false evidence," said Justice Aedit Abdullah.

The 43-year-old accused, a food stall assistant, was sentenced in 2017 to 23½ years' jail and 24 strokes of the cane for sexually assaulting his daughter.

The man, who cannot be named to protect her identity, was convicted of committing various sexual acts against her at home between the end of 2011 and April 2014, when she was between 11 and 13 years old.

A key element of the man's defence is that he could not have committed some of the alleged acts because his penis was deformed as a result of botched enlargement procedures.

A photograph of the man's penis, taken shortly before his trial began in November 2016, shows his misshapen genitalia, but the crux is whether these abnormalities existed between 2011 and April 2014.

When the girl and her mother took the stand, each made drawings that contradicted the photograph.

During his appeal in April last year, the man said he found two friends who can corroborate his story, although one eventually backed out.

The Court of Appeal sent his case back to the trial judge to determine the veracity of the new evidence, before his appeal hearing can continue.

During the further hearing, the witness, Mr Muhammad Ridzwan Idris, testified that he had seen the accused's penis in the toilet when they were working at a stall at the Singapore Expo in 2013.

He also made a drawing of the accused's penis that was highly similar to the photograph.

Mr Ridzwan said the two met again by chance in February last year.

After the man told him about the case, Mr Ridzwan told him he had seen his penis back in 2013 and agreed to testify for him.

But Justice Aedit did not buy the story.

The judge noted that after Mr Ridzwan told the accused about having seen his penis, the accused did not ask the witness what he saw.

"Given the significance to the accused of what the witness saw, what would have been expected would be at least some discussion and confirmation of what was seen," said the judge.

The judge also noted that Mr Ridzwan portrayed himself and the accused as acquaintances, but the prosecution submitted evidence that the two men had gone to Malaysia together several times.

The judge also had doubts about the drawing, of a top-down view, made by the witness.

He noted that Mr Ridzwan would not have observed a top-down view if he had been at a urinal next to the accused.

Generally, a match would support the case being put forward, he said, but the match here was "suspiciously close".

The judge concluded that the accused was involved in arranging for the false evidence to be brought to the court.

He said the fact that the accused came across two witnesses within a couple of weeks who saw his penis raises serious concerns about the veracity of the evidence.

Any consequence of the witness' false evidence would "have to be pursued separately, if at all", said the judge.

He also left it to the Court of Appeal to decide on the prosecution's arguments that the accused should get an extra 1½ years for abusing the court process.