Evidence of drug use. Policeman handling evidence of drug use during a raid on a flat. He is holding a piece of burnt aluminium foil, indicating that heroin has been used at the property. Heroin powder can be heated on tin foil above a flame, and the resulting smoke is inhaled through a small tube or pipe. This method of taking heroin is called 'chasing the dragon'. There is also evidence that heroin, or perhaps another drug such as cannabis, has been blended with tobacco and smoked in cigarettes (bottom left).