A TRANSPORT worker jailed for blackmailing a ''naive and gullible'' youth for $87,000 had his conviction quashed yesterday when the Court of Appeal held that the trial judge had seriously misdirected the jury. However, while ruling the conviction of Chan Wing-shing was unsafe and unsatisfactory, the court held it was proper to order a retrial. Chan's counsel on appeal, Peter Wan, submitted the trial judge misdirected jurors when he told them Chan's clear record was neither here nor there. The Appeal Court, comprising Vice-President Mr Justice Macdougall, Mr Justice Litton and Mr Justice Kaplan, agreed, holding that the trial judge's comment had deprived Chan the benefit of his clear record when the jury considered his credibility. Chan, 28, had denied blackmailing 19-year-old Lee Fook-peng, but was found guilty by a jury after a trial in March before Mr Justice Wong. He was sentenced to four years' jail. His co-defendant, Lam Wai-man, 25, had admitted one count each of blackmail and arson and was given a seven-year prison term. The Crown had alleged Chan and another man approached Mr Lee as he left a Macau casino after losing $4,200 on March 24 last year. Mr Lee allegedly agreed to borrow $5,000 from the men. Later the men allegedly claimed Mr Lee owed them $87,000. When Mr Lee failed to pay, several men allegedly went to his father's Wan Chai flat on April 30 last year. They were said to have poured petrol on the door and set fire to it while Lam acted as look out.