A NEWSPAPER vendor was yesterday sentenced to six years' jail after he admitted trafficking in heroin. Wong Lap-tung, 19, was seen by police carrying a brown envelope as he left his flat in Shek Yue House, Sha Tin, on June 15 this year. When confronted, he ran back to his room and dropped the envelope, which was found to contain 83 grams of No 4 heroin. Deputy Judge Wong told him the drugs trade should be eradicated and that to do so, ''all couriers have to be wiped off the street because it is couriers who make this trade flourish''. Because Wong was young and pleaded guilty at the earliest opportunity, the judge took a starting point of nine years and reduced it to six. Defence counsel Tim Kwok said Wong had become addicted to heroin and turned to trafficking to help finance his habit. He was not a professional drug courier.