On the first day of the resumption of the sex-for-grades trial, law professor Tey Tsun Hang, 41, continued to focus on proving that anti-graft officer Mr Teng Khee Fatt had "inflicted fear" upon him during interrogations last May.

Mr Teng was called again by the prosecution to the witness stand to produce a new piece of evidence - entry-and-exit records made by Cisco security officers manning the gates at the Corrupt Practices Investigation Bureau. The purpose was to clarify discrepancies that emerged during the trial in January between Mr Teng's investigation diary and taxi receipts Tey produced.

During cross-examination, Tey put to the court that Mr Teng had threatened him by saying: "You only got 1 per cent chance of survival. Try not to blow it up."

When Mr Teng disagreed, Tey reiterated: "The Defendant then got very distraught and pleaded with you. 'Why 1 per cent chance?'. And you smirked, "We close to 100 per cent success one you know."

Tey also alleged that Mr Teng had used Hokkien threats during the interrogation. Tey said Mr Teng had referred to his former student Darinne Ko, 23, as a woman "blanched but not cooked...you know, like wanton mee". Mr Teng disagreed.

Ms Ko is the former student at the centre of the sex-for-grades trial with Tey facing six counts of corruption of obtaining gifts and sex from Ms Ko in exchanges for better grades.

Chief District Judge Tan Siong Thye had earlier kicked off proceedings with a reminder to confine proceedings only to what is relevant to the charges.

Mr Teng stood down as a witness, and Tey took to the witness stand on Monday morning. A trial within a trial is ongoing to determine if statements Tey made with CPIB officers can be admitted as evidence.