Law professor Tey Tsun Hang and his former student Darinne Ko were lovers, said defence lawyer Peter Low on Tuesday, in his closing submissions for the sex-for-grades corruption trial against Tey.

Citing Ms Ko's testimony in court during the trial, Mr Low urged the court to adopt what she had said on the witness stand, rather than what she had told anti-graft officers earlier during their probe.

Arguing against Ms Ko's impeachment, Mr Low said her testimony in court had consistently showed that she and Tey were in a loving, intimate relationship from May to August 2010, which continued even after she went overseas for an exchange programme. "Though apart, the state of their relationship did not change. They were still lovers,"

Tey, 41, faces six charges of corruptly obtaining gifts and sex from Ms Ko, his 23-year old former student, in exchange for better grades.

The prosecution, however, shot down Mr Low's arguments and tried to show how Tey had "corrupt intent" and took advantage of his student.

Deputy Public Prosecutor Andre Jumabhoy said the relationship developed because Tey was "releasing to Ms Ko information which he was not supposed to", and because Ms Ko was impressed by him.

Mr Jumabhoy also pointed out that Tey had lamented about the loss of a prized pen and not having an iPod, which were "promptings" to Ms Ko, which led to her buying him a Mont Blanc pen and an iPod.

"By that stage, (Tey) realises this is a girl who will do what he wants," he said, and went on to show how Tey became more daring with his wants, including making her pay for his tailored shirts and a bill for a dinner he hosted.

Chief District Judge Tan Siong Thye will deliver his verdict on this case on May 28.