A basketball coach committed sexual acts on his then 13-year-old student and the teenager told his mother about his ordeal only two years later when he feared contracting a sexually transmitted disease.

Following a five-day trial, District Judge Mathew Joseph yesterday found the man guilty of committing two sexual offences in 2013 - sodomising the minor and performing oral sex on him.

The 57-year-old man cannot be named because of a gag order to protect the identity of the victim, now a 17-year-old polytechnic student.

In her submissions, Deputy Public Prosecutor Gail Wong said the man was the boy's reserve basketball coach when he was in secondary school. The teenager would go to the man's condominium in Bishan for basketball training, and was picked up from school by the coach.

During the trial, he testified he was in his coach's home some time in 2013 when the man carried him to a bed and sodomised him.

On another occasion, the coach put a pillow over his face and performed oral sex on him, he said.

No one else was at the house on both occasions.

The boy stopped going to the man's home later that year. He finally told his mother in 2015 as he was afraid of contracting HIV.

DPP Wong told the court he had asked her to take him for a medical check-up and later told her why. "This was the only time that she recalled the victim crying to her and he looked worried and anxious," said the DPP.

The boy made a police report on Feb 26, 2015, before taking a blood test. The results were normal.

The man is represented by lawyers R.S. Bajwa and Kertar Singh, who said the boy did not see his coach performing oral sex on him. The defence also said there was no evidence that their client had sodomised the teenager.

Judge Joseph said that "great lengths" were taken to observe the victim's demeanour while he gave evidence, and noted he was a reticent person who was "just being a teenager in giving his evidence, perhaps in not so eloquent fashion".

"(The accused) struck me as not being forthright, and even as being evasive at times."

In his testimony, the man claimed that he had no contact with the boy after August 2013.

He is out on bail of $30,000 and will be back in court on Jan 10.

•Additional reporting by Nicole Chia