For love or for grades?

The high-profile sex-for-grades case involving former National University of Singapore (NUS) law professor Tey Tsun Hang and his ex-student Darinne Ko took a surprising turn on Friday when the High Court acquitted him of corruption, after he had served a five-month jail term.

We look back at the case which had kept many riveted with risque details of their trysts, and surprising acts by Mr Tey during the lengthy trial.

* April 2012: Mr Tey, 42, was arrested after Corrupt Practices Investigation Bureau (CPIB) officers received a complaint that Miss Ko allegedly received favourable grades from him.

* July 2012: Mr Tey was charged with six counts of corruptly obtaining sex and gifts from Miss Ko, who was 21 years old then, between May and July 2010.

Miss Ko, who had a boyfriend then, lost her virginity to Mr Tey on a couch in his NUS law school office on July 21, 2010. They had sex again there four days later, on the eve of her 21st birthday. She later became pregnant but was told by Mr Tey to get an abortion and pay for it herself.

He also received gifts from Miss Ko, which included a $740 Montblanc pen, two tailored shirts worth $236.20, a $160 iPod touch, and a dinner at Garibaldi Italian Restaurant & Bar costing $1,278.60.

* January 2013: Trial began, with the star prosecution witness, Miss Ko, taking the stand on opening day.

* Defence's case:

Mr Tey, a former district judge, conducted his own defence, and initially did so wearing a black robe usually worn by lawyers in High Court hearings.

Mr Tey, who is married to a Japanese and has a daughter, said he was in a "mutually loving romantic relationship" with Miss Ko, and that the gifts and sex were par for the course.

Mr Tey also insisted that the statements he gave to CPIB officers had been made under duress and should not be admitted. In court, he sometimes re-enacted the threats by banging tables and repeating the expletives he claimed CPIB officers had said to him.

During the trial, he also stunned the court when he was seen crying, breathing heavily and retching what appeared to be saliva into a plastic bag on two occasions. The latter episode led to a two-week adjournment of the case.

* Prosecution's case:

The prosecution argued that Mr Tey abused his professional position for personal gain, and that Miss Ko was baited into buying him the gifts and tricked into having sex with him.

Miss Ko first met Mr Tey in January 2010 when she enrolled in his equity and trusts class. Their relationship had been "professional", she said in court, but blossomed after she started helping him in May that year with his research project for a book.

To thank her for the 80 hours of work she had put in, he took her out to lunch and they had a long chat which made her feel that they had a "connection". The two then started dating.

She tried to end the relationship after her boyfriend and parents found out about it, but soon resumed the relationship secretly because she missed him too much.

The prosecution, however, argued it was not real love on Mr Tey's part.

When Miss Ko discovered she was pregnant and told Mr Tey about the baby, she was told by him to abort it. He also claimed to have no money to pay for the abortion. In the end, Miss Ko paid for the abortion, even though she was just a student and Mr Tey was drawing a comfortable salary of $225,000.

* May 2013: He was found guilty, NUS terminated his appointment with immediate effect. Chief District Judge Tan Siong Thye, who rejected Mr Tey's defence, said it was "love with an ulterior motive".

* June 2013: Mr Tey was sentenced to five months' jail. He started serving his sentence.

* July 2013: Even as he was serving time, he was still fighting to prove his innocence. He instructed his lawyers to file appeals against his conviction and jail sentence.

* September 2013: He was given permission to serve out his jail term on home detention.

* October 2013: He was granted release from his jail term for good behaviour.

* Feb 28, 2014: The High Court acquitted him of corruption. Justice Woo Bih Li ruled that Miss Ko was in love with Mr Tey at the time, and that she was not trying to get better grades in return for having sex with him and showering him with gifts.

But the judge had strong words for the ex-professor, saying that he was "a man without honour", and that he had abused his position as a lecturer.