Blog: Polygraph testing & domestic violence – helping hand or Jeremy Kyle justice?

Jessica Ritchie, Lecturer in Criminology at the University of Northampton, has been following with interest the progression of a new Domestic Violence Bill, a draft of which includes the use of polygraph testing for offenders.

Here, she blogs about what this is and why its inclusion in the Bill is potentially harmful.

Recently, the draft of the Domestic Violence Bill was released and there are some interesting proposals – in particular, the use of polygraph testing for domestic violence offenders on conditional release from prison.

The proposed polygraph tests would be used to help determine the risk of an offender released into the community, or more specifically, their compliance with conditions of release and to improve management of offenders when released.

Polygraph tests measure respiratory rate, sweat gland activity, and cardiovascular activity (that of your heart and blood vessels) to determine whether deception is involved.

It is not, as may commonly be thought, a ‘lie detector’ test of the type you may see used in daytime TV relationship ‘discussion’ programmes.

Their inclusion in a Domestic Violence Bill is unhelpful and potentially dangerous.

For one thing, polygraphs can provide false results, through wrongly identifying an error where there is none, or not identifying an error at all (i.e. false positive errors and false negative results).

Some individuals participating in polygraph testing are able to use mental and physical countermeasures to reduce the accuracy of risk, such as controlled breathing and relaxation techniques or blood pressure controlling drugs.

On the other side of the coin, someone who has consumed a blood pressure increasing chemical, such as caffeine in a pre-testing coffee, could then ‘fail’ a polygraph.

Research suggests that even correctly conducted polygraph tests are only 70 to 90 percent accurate. Hence why polygraph results not being admissible in English Courts as they do not meet the standards for admissible scientific evidence.

Polygraph testing is already used for sex offenders on licence in the community, but there is no evidence as to whether this is effective in helping to manage them when they are out in the community. Of course, community safety is very important, and this is just one of the processes that are used to determine risk. However, to use polygraphs gives credence to a tool that is proven to have problematic accuracy rates.

It is good to see the government taking some initiative to attempt to tackle the critical issue of domestic violence. However, for high-risk offenders, there must be evidence-based measures used to undertake risk assessments to ensure community safety. One cannot help but think that the money used to administer these tests could be used in a much more constructive way – to further develop evidence-based risk assessment tools or evaluate current strategies so they can be improved.

Fortunately, other proposed amendments Bill are much more satisfactory. These include the use of protection orders to restrict offenders; requiring offenders to attend rehabilitation programmes when there is a substance abuse problem; special measures for victims in criminal courts; consideration of victims with complex needs and new measures to address coercive and controlling behaviour.

Transforming the Response to Domestic Abuse: Consultation Response and Draft Bill January 2019.