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Sweet Little Lies: The Surreptitious Spread of Police Polygraph Testing

With little public debate, and doubts about their reliability, Byline Times reveals the use of lie detectors is still increasing

Photo: Aleksei Gorodenkov/Alamy

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Police have spent at least £745,000 on “lie detector” test training and equipment with almost no public scrutiny, Byline Times can reveal. 

Freedom of Information requests show that at least 14 forces – one-third of the total in England and Wales – have paid money to the main UK trainer and supplier of polygraphs in the last ten years. 

While there has been little public debate on the matter, the use of the devices has been allowed in the criminal justice system since 2014. 

Many people associate “lie detector” tests with sensationalist talk show The Jeremy Kyle Show.  That was pulled off air in 2019 after a guest, Steve Dymond, took his own life after failing a test when asked if he had cheated on his partner. He insisted that he had not done so.  The then culture committee chair Damian Collins called its producers “irresponsible” for overstating the reliability of the devices to participants and viewers. 

Polygraphs work as their operators monitor bodily processes such as sweat and heart rate while questioning people. Major changes to those are believed to suggest dishonesty.  Critics say that while polygraph equipment can accurately measure some physiological activities, these aren’t proven to reflect a single process such as dishonesty and are not shown consistently among different people. Methods to beat the tests can also be learnt. 

Their evidence is not believed to be strong enough to be used in court, or in criminal investigations. 

Professor Ray Bull, an expert in forensic psychology, who gave evidence to the culture committee looking at the Jeremy Kyle Show and to the Litvinenko Inquiry, told Byline Times: “Because you plug it in and it’s some kind of gadget, you mustn’t be under the false impression that it’s accurate.” 

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In law enforcement, the devices were first used in 2014 with the probation service and police using them to quiz sex offenders as part of monitoring arrangements. Some offenders volunteer to be monitored, but others are made to take the tests as part of efforts to determine whether they pose a risk to the public or not. The Domestic Abuse Act 2021, and the Counter-Terrorism and Sentencing Act 2021 have widened its use to those convicted of domestic abuse and terrorism released on license. 

Marion Oswald, professor of law at Northumbria University, said: “It’s really being used as an interrogation technique, but without any of the safeguards that we would usually expect in our criminal justice system. 

“Like facial recognition and other technology, without clear standards and legal rules about polygraph testing by the police, citizens and even parliament can’t understand why and how the polygraph is being used, and what risks this poses.” 

FOI data supplied to Byline Times found that Northumbria Police was the biggest spender on the polygraph, paying £125,834 between April 2016 and the end of March 2023. Kent Police was the second largest with an £80,613 spend, with Norfolk the third biggest spender with £77,760.  Separately, the Ministry of Justice, which runs prison and probation services, has issued contracts worth a combined £2.6m for polygraphs since 2014. 

The College of Policing, the professional body for police in the UK, is working to establish national standards for the use of the devices.  Up to now, standards have been set by the polygraph training provider itself – a private company.  The College also plans to set up a facility to take over the training of police and other public bodies in its use, after concerns were raised by senior police that the provision of existing training is “inadequate”. 

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A spokesperson for the organisation said: “There is evidence polygraph can be effective in eliciting disclosures from some sex offenders. It is not used directly in legal proceedings – it is an intelligence tool to assist in managing those who pose a risk of harm to the public.” 

During a parliamentary committee in December the independent reviewer of terrorism legislation, Jonathan Hall said he had come to back the use of the devices in the wake of the 2019 attack at Fishmongers’ Hall by London Bridge. 

“Let us say that someone is in the community, they could be asked about their daily routine. The most likely outcome is that someone who is subject to a polygraph measure would feel that they have to tell the truth, and the evidence is that people who are subject to polygraphs make admissions. 

“That would give counter-terrorism police an amazing source of information to show that, contrary to what that person had been telling his probation officer, he was still in touch with [a] dangerous terrorist,” he said. 

This could enable new licence conditions to impose restrictions on potentially dangerous behaviour, he added. 

Professor Bull agreed that it is right that the College of Policing is developing standards but expressed concern about the potential wider use of the polygraph, given it is not accurate as a lie detector. 

“Given that the monitoring is ongoing, the people who do it ought to be properly trained and accredited, but is this the thin end of the wedge? Are the police going to get under the false impression that it could be used in the investigative setting? For me, that’s a real no-no.” 

The full amount spent by police on polygraph training and equipment could be higher than is currently known, as five forces did not respond to requests for information. And critics warn that the secrecy around their use needs to change. 

Professor Oswald said: “One of the things we’re really concerned about is lack of transparency and being able to get a clear picture of what is going on.  You shouldn’t have to put in requests about spending on training, this isn’t a covert tactic, it should be something that’s discussed in the open.” 

A Northumbria Police spokesperson said: “We have been using polygraph since 2016, when we became one of the first police forces in the country to make use of the technology.

“We use polygraph tests as part of our broader management of sexual offenders and their use is largely voluntary.

“The use of polygraph testing has proved to be a very useful tool and, as a force, we are keen to find and build on innovative ways to keep our communities safe.”


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