A Seoul court has handed down prison sentences for four members of a voice phishing organization suspected of manufacturing and supplying drug-laced beverages to students in a cram school district in Gangnam, Seoul in April.

The Seoul Central District Court on Thursday sentenced one of the four suspects, identified by the surname Gil, to 15 years in prison and ordered the forfeiture of two-and-a-half million won for violating the narcotics law. 

Gil is suspected of colluding with a China-based voice phishing group to produce 100 bottles of the drink by mixing ten grams of methamphetamine with milk and offering the drinks to 13 minors, claiming that the drink was designed to help increase concentration levels. Gil is also accused of attempting to blackmail the parents of six of the students, saying that they would report their children to authorities for drug use unless they provided hush money.

Another suspect, surnamed Park, who provided the methamphetamine to Gil, was sentenced to ten years in prison while two other members of the voice phishing group were given an eight-year and seven-year prison sentence, respectively. 

In issuing its sentence, the court said the suspects had committed a new type of crime that is a combination of a malicious crime seeking to profit by taking advantage of minors, voice phishing and drug crimes. 

Of the 13 students who were offered the laced-beverage, nine consumed the drink, six of whom experienced hallucination and other related symptoms.