The sex-for-grades corruption hearing was on Thursday adjourned so that Institute of Mental Health (IMH) doctors can assess if Tey Tsun Hang is fit to continue to stand trial.

The law professor was earlier in the morning diagnosed by National University Hospital (NUH) psychiatrists to have suffered an "acute hyperventilation episode" and prescribed Xanax to alleviate his anxiety.

This after court was abruptly adjourned after lunch on Wednesday as Tey appeared to be in a daze while under being cross-examined by the prosecution.

He was seen crying, breathing heavily and retching as he was assisted out of the Subordinate Courts by two female defence lawyers then.

Tey, who faces six counts of corruptly obtaining gifts and sex from former student Darinne Ko in exchange for better grades, was only discharged from NUH - where he underwent a battery of medical and physical examinations until the wee hours of the morning - at about 8.30am.

NUH psychiatrists had referred Tey to IMH for a forensic psychiatric evaluation, which will establish if Tey can continue to stand trial.

His latest 'panic attack' came after Deputy Public Prosecutor Andre Jumabhoy had produced an appointment card that contradicted Tey's court testimony.

Tey had claimed that he was forced to miss a psychiatric appointment with Dr Tommy Tan on April 10 last year by Corrupt Practices Investigation Bureau (CPIB) officers, because he had to give his statement, even when he had informed the officers about it.

CPIB officer Wilson Khoo, however, testified that Tey had only arrived - on his own accord - at 11.50am that day, and had "insisted" on giving his statement.

Mr Jumabhoy had produced evidence which showed Tey's appointment with the doctor was scheduled for 9.30am - well before he had even showed up at CPIB.