
UK POLITICIANS are considering new measures to combat domestic violence. Many elements of the government鈥檚 proposed Domestic Abuse Bill have been welcomed by campaigners, but it also includes a plan for those convicted of such offences to be regularly monitored after release with lie detector tests.
Lie detectors, also known as polygraph machines, measure changes in people鈥檚 pulse, sweating rate and other indicators, but they are notoriously inaccurate so it isn鈥檛 clear they can prevent reoffending.
The issue goes to the heart of a broader problem in the criminal justice systems of many nations. Very few crimes result in people spending the rest of their lives in prison, so sooner or later they are released 鈥 and our methods for attempting to prevent repeat offences lack scientific evidence.
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Prison treatment programmes based on psychological techniques are designed to cut reoffending, but it is unclear if they work. They may achieve nothing, wasting money, or even make it more likely that people will reoffend.
Such programmes have been around for decades. Early attempts were based on Freudian-style psychoanalysis, where people talk about their childhood. By the 1980s, these were being replaced with cognitive behavioural therapy (CBT), a form of counselling that aims to change people鈥檚 thinking patterns.
鈥淲e are trying to get offenders to stop and think instead of going straight to violence鈥
CBT is perhaps best known as a treatment for emotional problems like depression and anxiety. There is to show it can help with these conditions, but changing complex behavioural patterns such as criminal offending is another matter.
At first, CBT treatments in prisons were primarily aimed at sex offenders, but now they are used to tackle other crimes such as domestic violence. Programmes seek to help people understand the thinking processes and choices that preceded their criminal behaviour. They might include techniques for improving relationships with others and managing anger. 鈥淲e are trying to get them to stop and think instead of going straight to violence,鈥 says Richard Taylor, a forensic psychiatrist in London.
Unfortunately, we don鈥檛 know if this approach works. It isn鈥檛 that there have been no studies of these programmes, it is just that most are very poor quality, says Robert Forde, a former UK forensic psychologist and author of .
For example, many studies are too small to be useful, some looking at just tens of people. Or instead of measuring reoffending rates, they look at a proxy, such as impulsiveness reported through a questionnaire. After six months of therapy, the offender may know very well what answers they are supposed to give, says Forde.
Even studies that avoid these problems aren鈥檛 usually gold-standard randomised trials, but simply compare people who got the intervention with ones who didn鈥檛, without ensuring they had similar characteristics.

When one Canadian group tried to summarise the findings of all studies of a certain kind of sex offender treatment, they had to discard 105 out of 130 papers for . This analysis did find that treatment programmes were linked with lower reoffending rates, but other analyses disagree, including one from the Cochrane Collaboration in 2012, which looked only at randomised trials of sex offender treatments, and .
William Marshall, a retired psychiatrist and one of the early pioneers of CBT for sex offenders, believes it does work when done properly, but that key aspects are often dropped to cut costs. 鈥淵ou have to have people who know what they鈥檙e doing,鈥 he says.
Raising reoffending
Alarm bells rang in the UK after a large study of a CBT programme for sex offenders found it actually seemed to slightly raise reoffending rates. Out of nearly 16,000 men, 10 per cent of those who went through it carried out a sexual offence in the eight years after their release, compared with 8 per cent who hadn鈥檛 taken part. It wasn鈥檛 a randomised trial, but the researchers did carefully match those in the two groups to ensure fair comparison.
One explanation for the apparent rise is that the group therapy sessions involved could have helped to normalise the acts being discussed, according to a 鈥淲hen stories are shared, their behaviour may not be seen as wrong or different,鈥 said the authors. 鈥淎t worst, contacts and sources associated with sexual offending may be shared.鈥
When the results were made public in 2017, the UK dropped that particular programme and replaced it with two new psychological interventions called Horizon and Kaizen. But neither has been tested in randomised trials either. A government spokesperson says the programmes haven鈥檛 yet been around long enough to be tested, but evaluations are ongoing.
Other kinds of CBT scheme, such as those aimed at reducing violence, also suffer from a lack of evidence. A 2007 by the Ministry of Justice reviewed 11 studies and concluded that the approach is 鈥減romising鈥 鈥 yet six had no effect, while the others had basic design flaws.
That isn鈥檛 to say we should give up on prisoner reform. Classes or training can make it more likely people will end up in work on the outside. in three US states found that those who had taken optional educational classes as inmates had a reincarceration rate of 21 per cent, compared with 31 per cent among those who hadn鈥檛. And many jails offer counselling for drug and alcohol abuse similar to that found outside jail, such as the Alcoholics Anonymous 12 steps programme, which at least has supporting evidence that it reduces alcohol use in non-offenders.
While all UK prisons are supposed to offer these programmes, many inmates are unable to access them because of overcrowding or a lack of staff to escort prisoners from their cells, says Peter Clarke, the UK鈥檚 chief inspector of prisons. 鈥淭hat leads to boredom and people using drugs,鈥 he says. 鈥淭hat鈥檚 counterproductive in terms of rehabilitation.鈥
Frances Crook of the Howard League for Penal Reform, a UK charity, says even just making prisons nicer will cut reoffending. 鈥淚f you have got the best designed programme and it鈥檚 working really well, delivering that to someone sharing their cell with an open toilet and cockroaches on the floor isn鈥檛 going to work.鈥
鈥40%
Rate of reoffending among former prisoners in the UK鈥
Another problem is that parole boards have no good way to assess how likely people are to reoffend. These boards tend to place most weight on psychologists鈥 ratings of how much empathy or insight offenders have into their crimes, says Forde, who has acted as an expert witness in parole hearings.
This may be why discredited approaches like lie detector tests are increasingly called on. Such tests are already widely used in police investigations in many countries, although they aren鈥檛 usually admissible in court because of their known problems.
In 2014, the UK started using compulsory polygraph testing to monitor released sex offenders. A Ministry of Justice had shown that this technique raises the likelihood of people telling staff about incidents where they breached their parole conditions. 鈥淧olygraph testing isn鈥檛 just useful for detecting lies, but for encouraging offenders to tell the truth, to reveal more information than they might otherwise,鈥 said a spokesperson.
However, there is information online about how to cheat the test, and word is likely to get round among offenders, says Chris French at Goldsmiths, University of London. 鈥淚t produces too many false positives and false negatives.鈥
Now, as well as introducing the tests for those who have been convicted of domestic violence, the government plans to use them for terrorist offences, such as sharing videos that promote attacks. The prospect of releasing people jailed for these offences understandably triggers alarm. But the reoffending rate among convicted terrorists in the UK is far lower, at around 3 per cent, than that of other former prisoners, which is about 40 per cent, says Marc Sageman, a forensic psychiatrist at the US Foreign Policy Research Institute, who studies Islamic radicalisation.
For domestic violence, the UK probation service aims to try to evaluate lie detectors in a three-year pilot scheme of 600 offenders, half of whom will be randomly selected to take the test. Yet reoffending rates won鈥檛 be measured, which is a missed opportunity. To know whether any intervention works, you need randomly assigned test and control groups, and hard scientific data, says Sageman. 鈥淲e have learned that in medicine.鈥
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