The silent witness from tycoon Albert Yeung Sau-shing's trial went to the High Court yesterday in a bid to vindicate the decision to hold his tongue.
Last November, Michael Lam Yih-jiun, 31, was sentenced to six weeks in jail for contempt of court in refusing to testify against Mr Yeung, chairman of the Emperor Group.
Mr Yeung, 50, walked free last May after all five witnesses in his case mysteriously lost their memories.
Magistrate Paul Kelly ruled that Mr Yeung had no case to answer on one count of falsely imprisoning Lam and one of threatening to break his left leg.
Lam said he did not want to testify because he was 'very frightened'.
Defence lawyer James Chandler told the High Court that the magistrate had been closed-minded and biased: 'He's basically saying: 'You didn't know the rules, I didn't tell you what the rules are, and you are going to jail'.' But prosecutor Andrew Bruce said the magistrate's decision perfectly reflected the gravity of Lam's offence.