Offence categorisations as used in police recorded crime have always been broader than those used in court proceedings and the detailed returns on cautioning. From 1 April 2004, it was agreed that recorded offences of cannabis possession be separated from other drug possession offences to better monitor the use of police powers to issue cannabis warnings. It has not been considered necessary to record more detailed breakdowns on other drug possession offences as overall detection rates for these offences are high.
Information on court proceedings and cautioning give a good picture of the extent of other drug possession offences that come to the attention of the police by type of drug.