A CONSTRUCTION site worker who succeeded in having his conviction on a drug charge quashed on appeal in August managed to get a much reduced sentence when he decided to plead guilty at his retrial. Sentencing Tam Chun-fai to seven years in jail, Deputy High Court Judge Daniell used 12 years and nine months as a starting point and allowed a discount for Tam's co-operation with the police and his guilty plea. Tam, 31, had been found guilty by a jury in October last year on a charge of trafficking in dangerous drugs and was sentenced to 13 years in jail by Deputy Judge Wong. The conviction was overturned on appeal but a re-trial was ordered. When he appeared before Deputy Judge Daniell for retrial earlier this month, Tam admitted the offence, and sentence was passed yesterday. The court heard Tam was intercepted by police on November 10, 1992. A total of 251 grams of heroin with an estimated street value of $178,000 was found in the paper bag he was carrying. His counsel, Sze Kin, in mitigation, said her client started to take drugs at 15. At the time of the offence, he had been arrested for possessing heroin for his own use and was desperately in need of money.