Law enforcement authorities in the UK conducted an experiment in policing in the London borough of Lambeth, wherein cannabis violations were given a low priority. Researchers for PRS Consultancy Group undertook an evaluation of the program at the request of the Borough Police Commander. The researchers found that:
"The measures of police activity demonstrate that the policy has succeeded in releasing resources, and that activity against more serious offences has increased.
"During the 6 months of the evaluation, Lambeth officers issued 450 warnings. This released at least 1350 hours of officer time (by avoiding custody procedures and interviewing time), equivalent to 1.8 full-time officers. A further 1150 hours of CJU staff time was released by avoiding case file preparation.
"In comparison with the same 6 months in 2000, Lambeth officers recorded 35% more cannabis possession offences and 11% more for trafficking. In adjoining Boroughs possession offences fell by 4% and trafficking fell by 34%.
"Lambeth also increased its activity against Class A drugs relative to adjoining Boroughs."

Source

PRS Consultancy Group, "Evaluation of Lambeth's pilot of warnings for possession of cannabis - summary of final report," March 2002, p. 1.
http://www.ukcia.org/research…