IT IS over. Nominated MP Thio Li-ann will not be suing playwright Alfian Sa'at for a strongly-worded email he had sent her.

'I consider the case closed,' she told The Straits Times on Wednesday.

One reason is that Mr Alfian had sent her an email apology on Wednesday morning that was 'civil'.

In it, he wrote that he had looked through the Hansard parliamentary records and noted her speeches on other issues such as women's rights and the elected presidency.

Prof Thio said another primary motivation for her decision is that she wants to live by her espoused principles of the need for robust debate in a democracy.

Said the National University of Singapore law academic: 'In my academic writings, I have argued, in relation to defamation case law, for more protection to be given to 'political speech' by requiring public figures or politicians to be 'thicker-skinned', in the interests of robust democratic debate.'

'That is a primary motivation for not pursuing the matter further - living by my political liberal principles of the centrality of rigorous and vigorous debate for the health of democratic debate.'

She added: 'I don't believe anyone should be trigger happy with political defamation suits.'

The episode began when Mr Alfian, thinking Prof Thio had made a police report leading to the cancellation of a National Day picnic organised by gay activists, sent a four-line email to her 'in a flash of anger'.

It contained a four-letter word and accused her of 'hatemongering' and 'vicious crusades against sexual minorities'.

Prof Thio made a police report, and cited the email in Parliament last week during the debate over the repeal of Section 377A, describing it as being 'full of vile and obscene invective'.

Mr Alfian later posted the email on his blog, identifying himself as its author.

Read the full report in Thursday's edition of The Straits Times.