SINGAPORE - A 24-year-old man who took up an offer from another man to join two sexual trysts with the latter's girlfriend without her knowledge and consent was convicted of rape and other sexual offences on Friday (June 26).

The High Court rejected the defence of Srihari Mahendran, who said he believed that the woman, blindfolded on both occasions, had consented to having a threesome.

Justice Pang Khang Chau said text messages between the two men, a video recording of the sex acts and hotel surveillance footage indicated that Srihari knew that the plan for him to join the couple was to be kept a secret from the woman.

The judge also found the boyfriend, a key prosecution witness, to be a reliable witness who had no clear motive to falsely implicate Srihari as he had already been sentenced.

The 28-year-old boyfriend, a former auxiliary police officer, is serving a jail term of 19 years and 11 months for abetting Srihari to rape and sexually assault the victim.

He cannot be named due to a gag order to protect the identity of his former girlfriend, now 29.

The boyfriend testified that he wanted to indulge his fantasy of engaging in a threesome with his girlfriend and another man, but she rejected the idea when he floated it to her.

He then hatched a plan to secretly bring another man into the hotel room to have sex with her, while he watched and filmed the acts.

He was able to carry out such a plan because the couple engaged in sexual practices which involved the woman being bound and blindfolded.

On the night of April 29, 2016, the man let Srihari into a room at Hotel 81 Bugis while she was bound and blindfolded.

In the second incident on Aug 7, 2016, he again had Srihari join them at the M Social Hotel in Robertson Quay.

This time, she sensed something was wrong and removed her blindfold to catch a glimpse of a person leaving the room. Both men were later arrested at the hotel.

Justice Pang found Srihari guilty of four counts of rape, one count of sexual assault by penetration, four counts of outrage of modesty, and one count of making an obscene film.

The judge noted that the video recording of the Hotel 81 incident showed that there was absolutely no verbal communication between both men.

The boyfriend had also made moaning sounds while Srihari was having sex with the woman.

This showed that there was a need to hide from her that there was a second man in the room, said the judge.

He also pointed to text message exchanges between the men. In one, the boyfriend said he would allow Srihari to have sex with her "secretly".

In another, he told Srihari to "sneak in after she sleeps".

Justice Pang said: "This is clear evidence that the accused knew that their plans were to be kept secret from the victim."

CCTV footage from the M Social Hotel also showed Srihari leaving the room in a hurry and running towards the lift lobby.

"Clearly, the accused knew that his presence in the room was not supposed to be known by the victim," he said.

The case was adjourned for sentencing.

Bail was increased from $50,000 to $60,000 and Srihari would have to wear an electronic tag until he is sentenced.