Preventive Measures in Controlling illicit Drug Usage and Trafficking : A Critical Analysis of the Sri Lankan Situation, International Conference on Exploring Linkages between Drug Usage and Criminal Victimzation, Conducted by INCDCV with Corroboration of DOCCJ and Department of Criminology and Criminal Justice, Manomaniam Sundarnar University, Tirunelveli, Tamil Nadu, India, March 08-10 2012