The effectiveness of three types of plastic bags used by the New South Wales Police Force for the storage of clandestine drug evidence has been investigated through a comparison of mechanical properties.The tensile and tear properties of “as received” low-density polyethylene (LDPE) and poly(vinyl chloride) (PVC) bags do not show major differences such that one type would be favoured over the other.However,the mechanical properties of the bags once exposed to a range of chemicals routinely collected as drug evidence have been shown to be influenced as a result of different chemical interactions.Although an interaction of reagents/solvents with an additive within the LDPE bags is proposed to influence the mechanical properties of the bags,the change in properties has been shown to be less severe than that observed for the PVC bag,where softening and damage of the bags results due to absorption of reagents.