NUS Law professor Tey Tsun Hang arrived in court Thursday morning, barely five minutes before his sex for grades trial was to start at 9.30am.

His former student, Darinne Ko Wen Hui, 23, who is expected to appear as a prosecution witness on Thursday, was not seen entering the courts Thursday morning.

Speaking to reporters in the lift as he made his way to the courtroom, Tey said: "It's a busy day for everyone."

Tey, 41, faces six charges of having corruptly obtained gifts and sex from his former student, Ms Ko, in exchange for good grades. He is represented by lawyer Peter Low who arrived at the courts at about 9am.