How many prisoners are drug addicts?
Keith Vaz, Chair, Home Affairs Committee: "The problem is that 35% of those in prison have a drug addiction and 6% acquire that addiction once they are in prison, so more come out with an addiction than went in with one."
Jeremy Wright, Prisons Minister: [separately] "It is important to recognise that the rate of mandatory drug testing producing a positive result has dropped considerably, from 25% or so in 1996-97 to about 7% now."
It won't come as much surprise to hear that the prison system in England and Wales has a drug problem. But how big? And are things on the mend?
Fewer prisoners testing positive...
According to the Prisons Minister, the answer to the second question is yes. The National Offender Management Service uses what's called 'random mandatory drugs testing' to measure the level of drugs misuse in prisons. It takes a sample of 5-10% of the inmates of a prison each month and gives them a clinical drugs test.
Jeremy Wright points out that the positive result rate from these tests has fallen from about a quarter in 1996/7 to 7% in 2011/12. This is right - the Ministry of Justice's (MoJ) said as much in evidence to the Home Affairs Committee last year, and MoJ management information has show a steadily declining rate from 9% a few years ago.
...but
There's some reason to doubt the accuracy of these figures. A Home Office study from 2005 found that the testing "underestimates the overall prevalence of use." For instance, the report points out that there's a high threshold for detection to minimise false positives, and refusals to partake in the tests aren't included "even though they might be expected to occur when a prisoner knows they will test positive."
Another problem is that mandatory testing doesn't detect the abuse of prescription drugs. The Chief Inspector of Prisons commented last year that:
"prescription drugs are not routinely detected under current mandatory drug testing procedures which therefore understate the availability of abused drugs in prison.
"Diverted medication is now reported in the majority of prisons we inspect, resulting in problems such as drug debts, bullying, unknown interactions with other prescribed drugs and the risk of overdose."
So while the Minister rightly quotes his statistics, they don't necessarily describe the full extent of the problem.
Over a third of prisoners are 'problem' users
Keith Vaz meanwhile highlights the problem of drug 'addiction' in prison. This isn't easy to measure. Most statistics from the Ministry of Justice, or those compiled by the Prison Reform Trust relate simply to the prevalence of drug use in prison rather than addiction specifically.
For instance, 70% of offenders have reported misusing drugs before entering prison, while last year the Prison Inspector's own surveys found that 24% of prisoners reported that it was easy or very easy to get hold of drugs in their prison.
There has been research on 'problem' drug use however from both the Prisons Inspector and the now defunct UK Drugs Policy Commission (DPC). In 2010 the former found through surveys that 29% of prisoners said they had a drug problem when they arrived and a further 6% said they'd developed a problem since arriving. This is the likely to be the source of Mr Vaz's claim.
Similarly, the DPC found in 2008 that between a third and half of new receptions to prison were estimated to be problem users, equivalent to between 45,000 and 65,000 prisoners in England and Wales.
However what these show is that prison itself isn't predominantly a place where offenders start their drug abuse habits. Instead, most prisoners who could be defined as having or having had a drugs 'problem' had it before they even arrived, and evidence suggests substantial numbers still find it easy to get their fix while behind bars.
There's some research which suggests that the problem may be waning as prison services seek to provide more treatment facilities and tougher enforcement, but in this regard the evidence base rests on shaky ground. Drug testing is most likely to underestimate the extent of the problem, so if anything the figures might give us a more positive picture than is justified.