Sherlock Holmes and the Drug War
A combination conspicuous for its absence. The crimes Sherlock Holmes unravels pertain to theft and murder, motivated by the usual assortment of human passions. Drugs are present neither as a crime themselves, nor as motives for other crimes.
(At least to my recollection, but it's been awhile since I read through all the stories. DOB and I are reading through them at the rate of about one a month, so it will take me awhile before I have a more definitive thought on this.)
To be sure, literature is not criminal statistics, but nothing conveys the mores and social realities of a time better than its literature. Sherlock Holmes is meant to be sensational--to tell the tales of the dregs of society. So it ought to be an excellent place to look to see how drugs influenced Victorian England.
Drugs were readily and legally available at the time. Opium dens operated; Holmes himself shoots cocaine from time to time when the casework gets slow. It's not evident from Sherlock Holmes, but opium and cocaine were commonly used in patent medicines.
And the dangers of drugs were known. Watson lectures Holmes from time to time on his cocaine use, rather as a doctor might today lecture a patient on smoking. In one story, Watson must go to an opium den to retrieve a friend who is tragically addicted, much to the grief of his friends and family.
But drugs still are not perceived as a societal problem per se. Certainly they sometimes cause problems for individuals, but even there the drug of choice for home-destruction is alcohol. (As it has been since Noah planted a vineyard and will be until the cup is passed in the New Jerusalem.) Because drugs are legal, they do not attract the attention of organized crime. Imagine what Professor Moriaty could do if he also headed up a drug cartel.
In short, the record of Victorian England gives us historical precedent that the legalization of drugs not only means no need to prosecute people for having drugs, but also gets rid of crimes committed over drugs--and without an increase in drug abusers. Then today's police, like Sherlock Holmes, could focus on thieves and murderers and let the mere addicts alone.