Two frightened witnesses who put a drug queen behind bars for 30 years had their own sentences for trafficking slashed by the Court of Appeal yesterday. Siu Chun-chung, 35, and Tan Fu-jung, 46, betrayed mother-of-two Poon Lai-lin, the mastermind behind a heroin empire which flooded Hong Kong with drugs. Now they fear the 34-year-old may use her wealth and underworld connections to take revenge on them and their families. Siu's jail term was reduced from 14 years to 11 years and Tan's from 18 years to 11, after the judges were told the police backed their bid for leniency. The pair, who were originally warned their crimes warranted 28 years in jail, smiled broadly as they walked back to the cells. Andrew Macrae, for Siu, said both men were serving their sentences under tight security. 'They have brought to justice very important figures involved in crimes of the first order of gravity. They have placed themselves in extreme danger for many years to come,' he said. Mr Macrae told the court it was rare for the generals and lieutenants of vast drugs syndicates to be convicted. It was vital to encourage their criminal associates to come forward and give evidence against them. Poon, whose husband is facing execution in China for trafficking, was jailed in November for smuggling 106 kilograms of heroin worth $100 million into Hong Kong. Her 'able lieutenant' Leung Wai-yat, 40, was given a 25-year term for dealing in 36 kg of the drug. The prime witness against the pair was Siu, a loanshark and triad 'red pole fighter', or captain, who had helped deliver drugs. They could not have been convicted without his evidence. Tan had persuaded Siu to become a prosecution witness and give evidence which backed his testimony. Both admitted dealing in 13 kg of heroin in Tai Po in March 1995.