Drugs, Prisons and ‘Unintended Consequences’ – Does drug interdiction drive drug-related harms?

Rick Lines, Olivia Howells and Daniel Webb*


The availability of drugs in prisons around the world is well documented. In Europe alone, up to seventy percent of people in prison have used an illicit drug. In Canada, forty-eight percent of prisoners in federal correctional institutions have had ‘problems’ with drugs. In Australia, one in six people discharged reported using illicit drugs during their sentence.

The 2018-19 Annual Report of HM Chief Inspector of Prisons for England and Wales stated, ‘we are regularly told how easy it is to get hold of illicit drugs in prisons, and of the shockingly high numbers who acquire a drug habit while they are detained’. The Chief Inspector was ‘particularly concerned by the high number of prisoners who said they had developed a problem while in prison – 13% of adult men in our survey reported that they had developed a problem with illicit drugs since they had arrived’. Here in Wales, a Cardiff prison survey found that fifty-two percent of prisoners said it was easy to get illegal drugs into the prison.

The availability and use of drugs in prisons cannot be separated from wider drug policy. The criminalisation of drugs and the people who use or sell them fuels mass incarceration in many countries, and in doing so creates large profitable markets for drugs behind bars. To counter this, prison systems around the world have deployed a wide range of supply reduction and drug interdiction measures – from searches to sniffer dogs to drug testing – to try to stop drugs entering prisons, and to disrupt internal markets.

Are these measures effective at deterring drug use or shrinking illicit markets? The high levels of drug use in prison cited above suggest the impacts are limited at best, and that despite the efforts of prison security, drugs continue to flow into places of detention with relative ease.

Photo by Matthew Ansley on Unsplash

Although supply reduction efforts in prisons may be ineffective overall at eliminating drug markets, that does not mean they do not have an impact on drug consumption. As noted in 2008 by Antonio Maria Costa, former Executive Director of the UN Office on Drugs and Crime, efforts to control illicit drugs often have negative ‘unintended consequences’ not considered at the time they were implemented. In other words, drug enforcement efforts often have the effect of creating problems worse than those they were intended to solve. In prisons, one of these ‘unintended consequences’ is increased drug-related risk and drug-related harms.

One widely used measure to deter drug use in prisons is mandatory drug testing (MDT). The UK Ministry of Justice states that 67% of prisoners surveyed in 2014/15 had participated in some form of MDT. While the UK government states that MDT is intended to ‘deter prisoners from misusing drugs’ and to ‘contribute to drug supply reduction, and contribute to prisoner safety, violence reduction, order and control’, the evidence suggests that random drug testing may actually undermine all of those objectives.

Cannabis is the most commonly used drug by people in prison in the UK, with a reported 79% lifetime prevalence of use. It is also a drug that remains highly detectable in the body for long periods after use. As such, cannabis users in prison have a ‘high risk of detection through mandatory drug tests’. One of the ‘unintended consequences’ of MDT in prisons is therefore a switch from cannabis use to heroin use among prisoners. As heroin is undetectable via MDT after only two to three days, heroin use becomes a logical choice for people who want to use drugs and minimise their risk of being caught. This switch to heroin use can also lead to a switch from smoking to injecting as a route of administration, with the attendant risks of blood-borne virus transmission and vein damage from sharing and reusing scarce injecting equipment in prisons.

There are also increasing indications that drug interdiction activities in prisons are driving the availability and use of new psychoactive substances (NPS), with mandatory drug testing again playing a role. Many varieties of NPS are not detectable by drug testing, creating an incentive to choose new psychoactives as a way to minimise risk of detection. As noted by one observer, ‘due to testing…cannabis, which is argued to be a lower risk substance, has been replaced by spice – a substance perceived to have more dangerous health implications’. A study commissioned for the National Offender Management Service found that prevalence of synthetic cannabinoids was twice as high among prisoners at time of release than at the time of admission. In that study, synthetic cannabinoids were the only substance for which a higher prevalence was detected upon release than upon admission, suggesting a statistically significant uptake of use of NPS by people in detention.

The European Monitoring Centre on Drugs and Drug Addiction (EMCDDA) has noted that ‘the avoidance of positive drug tests has been suggested as motivation for drug users to switch to NPS while in prison’ and that ‘increases in NPS use in prisons may therefore, arguably, be an unintended negative consequence of random mandatory drug testing programmes in some European prisons’.

While the UK and Germany have recently incorporated detection of synthetic cannabinoids into its MDT programme, this ultimately will not address the issues of drugs in prisons, or the creation of risk. As noted by EMCDDA, ‘One possible outcome…is that there may be displacement from use of synthetic cannabinoids to other substances, such as synthetic opioids, which may also be extremely harmful.’ Indeed, the EMCDDA notes that the use of synthetic opioids in Latvian prisons ‘has been accompanied by more overdoses and an increase in injecting, including needle-sharing’.

The UK Prison Inspectorate has stated that ‘NPS have created significant additional harm and are now the most serious threat to the safety and security of the prison system’. The widespread use of NPS, driven in part by random drug testing, suggests that the MDT is having the opposite effect of that intended by the government. In 2005, MDT was withdrawn from Scottish prisons as it was deemed a waste of funds that had little effective impact on drug use amongst prisoners.

Such negative ‘unintended consequences’ can also be identified from other supply reduction efforts. Drug detecting sniffer dogs are widely used throughout the UK prison regime. A 2014 review of supply reduction activities in Australian prisons described the impact of sniffer dogs as ‘modest’. However, even this ‘modest’ success is undermined in the case of new psychoactives. The EMCDDA, for example, cautions that, ‘Sniffer dogs are not trained to recognise the many different types of NPS.’ The UK Prison Inspectorate has noted that ‘Synthetic cannabis has no distinctive odour and is therefore harder to detect than non-synthetic cannabis, making it more attractive to smuggle in’. Even where dogs are trained specifically to identify one type of NPS, such as ‘Spice’, the longer-term effectiveness of this is made difficult by ‘the ever-changing composition’ of new psychoactives, making the programmes ‘ineffectual’.

Drug use is as much a part of the prison environment as it is the outside community. Overall, the supply reduction activities of prison regimes fuel drug-related risk and drug-related harms among people in detention. The advent of NPS only exacerbates this, creating an environment in which use of new psychoactive substances, substances often more dangerous than the traditional drugs they are created to mimic, are the easiest to smuggle in, and the most logical to use if wishing to avoid detection.

If governments are truly serious about addressing drug use and reducing drug-related harm, they must move away from enforcement-focussed responses, and instead implement laws and policies that reduce the number of people in prison for drug-related offences, and to provide comprehensive harm reduction programmes for people in detention.


*Dr Rick Lines is Associate Professor of Criminology and Human Rights at the School of Law, Swansea University. He is also a Senior Research Associate with the Global Drug Policy Observatory. Olivia Howells is a Law and Criminology student at Swansea University and Daniel Webb  is a Criminology and Criminal Justice student at Swansea University.

This research was conducted as part of the Swansea Paid Internship Network programme, a scheme enabling School of Law students to obtain experience working on an active research project under the guidance of an academic supervisor.