It is not an offence to possess magic mushrooms in their natural state. However, psilocin and psilocybin, the drugs that they contain, are Class A drugs. So if the mushrooms are intentionally prepared by, for example drying, freezing or pickling, then you might be charged with possession, supply, intent to supply or even production. The main offences The most common offence is possession of a controlled drug. This includes joint possession of a common pool of drugs and past possession, when past drug use is admitted.
More serious offences are supply and intention to supply.
Remember, supply includes giving or selling drugs to a friend, or even looking after them for someone else. People who say, 'the drugs were not all for me, some were for a friend' usually make things worse for themselves by admitting supply. The heaviest penalties under the law concern the import and supply of controlled drugs. Making or growing your own Cultivation of cannabis is also an offence. Penalties are more severe if the court believes cultivation was intended to supply others.