VISAKHAPATNAM: Visakhapatnam city is the leading producers of cannabis in the country. The conviction rate in ganja trade cases is low, estimated at about 5 to 10 per cent. The hands of the enforcement officials are tied up due to lack of evidence against drug smugglers and most of the cases related to ganja trade have ended in acquittals due to this, say legal experts. Over the past few years cases booked against ganja smugglers are rising.