A 55-year-old man, who was accused of sexually assaulting his stepson when the younger man was between eight and 17 years old, was yesterday acquitted of 13 charges involving various sexual offences.

But he was convicted of two other charges, for stalking his stepson's girlfriend and for criminal intimidation by pointing a chopper at his wife and threatening to kill his stepson.

The man, a former supermarket storekeeper, was sentenced to a year's jail on these two charges. The jail term was backdated to Dec 3, 2018, when he was remanded in custody.

In clearing the man of the sexual offences allegedly committed between 2007 and 2015, High Court Judge Chua Lee Ming listed "numerous and extensive" inconsistencies in the stepson's account.

Justice Chua said: "The complainant's testimony in court is inconsistent with statements that he had made to the police in 2016 and 2017, and in particular, his conditioned statement which he had signed on Dec 28, 2019, just six months before he gave evidence in court."

He said that, viewed in totality and in context, the inconsistencies give rise to grave doubts about the credibility of the stepson's evidence.

The judge also noted that the stepson had testified that the sexual activities started in 2007 and continued from January to March 2010. But the accused was in prison from May 2009 to March 2010.

Justice Chua also noted that there were five adults and one baby living in the family's one-room flat until March 2010, save for four months in 2008.

"I accept that not everyone would have been at home at the same time. Nevertheless, I have doubts about the complainant's allegations that the accused frequently engaged in sexual activities with the complainant at the flat," he said.

The stepson, who is now 22, reported his stepfather to the police in 2016 after the older man harassed his girlfriend.

He told police that his stepfather had groomed him to engage in sexual activities since 2007, when he was in Primary 3.

The acts escalated from fondling to oral sex and sodomy, he said.

He said he became aware that it was wrong and stopped the sexual activities in 2014, when he was in Secondary 4.

He said that in October 2015, after he brought his girlfriend home, his stepfather demanded that they resume their sexual activities.

Between October 2015 and January 2016, the accused sent numerous text messages to the girlfriend, waited for her at the foot of the block of flats where she lived and even confronted his stepson when he saw the couple together.

The accused, who was defended by Ms Sadhana Rai and Mr Pramnath Vijayakumar, contested the charges in a trial that began in June last year.

Yesterday, Mr Vijayakumar told the court that the man has apologised to his wife for pointing the chopper at her.