Professor Alex Stevens:

It is not unique to that offence. With most offences, only a very small proportion of them lead to a criminal justice outcome with murder being an exception in that they are very often apprehended. Let us take a really emotive example - and I always hesitate to do this - of sexual offences and rape. The reporting rate is increasing and in my country the detection rate is minuscule. The proportion of people who are accused and who actually get convicted is very small. That is not an argument for decriminalising sexual offences and rape. Deterrence is not the only reason that we criminalise certain offences. Some offences we criminalise because they are inherently wrong and we want to send that message. Whether someone thinks that drug possession is inherently wrong is a matter of opinion but for me and many others - indeed the millions of people who are taking drugs - it is not inherently wrong and they are not in any way near to causing the amount of harm directly to other people that sexual offences and rape do. If we accept the position that people have the right to choose what to put in their own bodies, absent any harm to other people, we are only left with the argument of deterrent.