Can you beat a lie detector? UK police increasingly using polygraph tests – here’s how people try to cheat
I’m officially a bad liar.
With a blood pressure cuff pumped tight around my arm, straps around my chest monitoring my breathing, and sensors on my fingers to pick up any traces of sweat, veteran polygraph test examiner Don Cargill says he can easily spot the signs I’ve told him a fib.
I’ve denied writing the number three on the piece of paper placed underneath my chair, in a simple exercise designed to show how my body reacts to lying. Even with nothing to lose, it’s an uncomfortable experience.
But while commonly associated with daytime television programmes like The Jeremy Kyle Show, the use of lie detectors is expanding within the criminal justice system.
And the answers people give could help determine whether or not they can see their children – or even land them back in jail.
Lie detector tests featured regularly on The Jeremy Kyle Show. Pic: ITV
In an office above a branch of Carpetright in west London, Mr Cargill carries out private polygraph tests. His clients have included foreign politicians accused of bribery, bodybuilders who want to prove they haven’t taken performance-enhancing drugs, and people accused of stealing from their family or being unfaithful to a spouse.
More and more are trying to cheat the polygraph using instructions found online, he says. “There’s a lot of techniques they do but we spot 90% of them or more.”
I’m asked to jump up and down and open my mouth before my test. Some people have pressed drawing pins into the bottom of their shoes, or even superglued tacks in their mouths, to create a pain response in their brain to distort the chart, Mr Cargill says.
He asks for identification to make sure a stand-in hasn’t been sent and carries out other simple tests to spot signs of sleep deprivation or illegal drug use.
A camera is trained on the subject’s eyes to make sure they don’t cross them or “zone out”, while a seat pad is in place to catch out anyone clenching their bottom.
All of these methods have been used to try to cheat the test, Mr Cargill says.
Sky’s Henry Vaughan takes a lie detector test
Can lie detectors be cheated?
It is possible to beat the polygraph, says Newcastle University Emeritus Professor Don Grubin, but it takes a lot of practice with the equipment and examiners are trained to spot the signs of anyone trying to trick the test.
Double child killer Colin Pitchfork – who was jailed for life after raping and strangling 15-year-olds Lynda Mann and Dawn Ashworth in Leicestershire in 1983 and 1986 – was recalled to prison in 2021 partly due to concerns he was using breathing techniques in a bid to beat the lie detector.
The Home Office says the polygraph records physiological changes in a person, quoting research from the American Polygraph Association which found deception is accurately detected in 80 to 90% of cases.
Since 2014, probation services have carried out more than 8,800 polygraph tests, while police have conducted more than 4,600, says Prof Grubin, who explains around 60 to 70% result in disclosures – where someone reveals relevant information.
His company, Behavioural Measures UK, has trained and supervised dozens of police and parole polygraph test examiners over the past decade, and like other experts in the field, he doesn’t like the term lie detectors.
The technology detects the “cognitive process” (or the brain working harder) when someone tells a lie, he explains.
The results of a polygraph test
The “real skill lies in the experience of the examiner”, says Mr Cargill, the chief executive of VAST Screening Technologies Ltd and the chairman of the British and European Polygraph Association.
“Nervous reactions are completely different from people telling lies,” he says. “Your heart rate physically increases because you’re triggering the autonomic nervous system, which triggers a fight, flight or freeze response. You want to run away.”
But critics, including University of Northumbria researchers Dr Marion Oswald, a professor of law, and associate professor Dr Kyriakos Kotsoglou, say much of the research is carried out by the industry itself and the accuracy can’t be tested in a real-life situation – because it is impossible to verify if someone has told a lie.
They say it is an intrusive “interrogation” technique used to illicit confessions, arguing the polygraph device itself is unnecessary and could be swapped for putting someone’s hand on a photocopying machine – a method apparently used by Detroit police and immortalised in cult American crime drama The Wire.
“If you can convince the subject that she or he is being monitored for lies and they believe it, then she or he will disclose more information,” says Dr Kotsoglou.
How are lie detectors used?
The results can’t be used as evidence in criminal courts but mandatory lie detector tests have been used as a licence condition for sex offenders since 2014, then rolled out to convicted terrorists in 2021 in the wake of the Fishmongers’ Hall attack.
They are also used by police and the security services to monitor the small number of terror suspects made subject to Terrorism Prevention and Investigation Measures (Tpims).
There is currently a three-year trial for their use on domestic abuse offenders, while the new Criminal Justice Bill proposes to extend this to convicted murderers who pose a risk of committing a relevant sexual offence on release.
The tests provide “invaluable information we would otherwise not have had about offenders’ behaviour which helps us to better protect the public”, the Ministry of Justice says.
The Metropolitan Police is looking into using lie detection technology to vet new recruits or root out corrupt officers following a string of damaging scandals, including the cases of Sarah Everard’s murderer Wayne Couzens and serial rapist David Carrick.
David Carrick and Wayne Couzens
But “this is still at an early research stage” and there are no imminent plans to use the technology in this way, the force says.
Others are turning to lie detectors to try to prove their innocence.
Kevin Duffy, 70, passed a polygraph test after he was convicted of sexually assaulting a child, but the results weren’t taken into account by the judge who jailed him for more than nine years.
His son Ryan Duffy, 44, says: “If there’s something that can be used when it’s one person’s word against another’s that can highlight some kind of evidence, why can’t it be used?
“If they are prepared to look at it after conviction for single case issues such as, ‘are you using public transport, hanging around schools’, and relying on data for probation services, then why can’t you use it beforehand?”
Kevin Duffy took a polygraph test to try to prove his innocence. Pic: Ryan Duffy
People can’t be sent back to prison for failing a test, but they can face further sanctions, such as stricter licence conditions, and they can be recalled for making disclosures that reveal they have breached licence conditions or indicate their risk has increased.
The information gathered can be shared with police to carry out further investigations, which could lead to charges, while those found trying to trick the polygraph can also be recalled to prison.
A government report last year revealed four convicted terrorists were sent back to jail as a result of lie detector tests – three were recalled after disclosing “risk-related information”, while the fourth didn’t comply with their polygraph licence condition.
Sensors pick up any traces of sweat during the polygraph test
An increasing number of police forces are using the polygraph, which is seen as a useful tool to monitor and assess the risk of people on the sex offenders’ register, allowing officers to concentrate stretched resources on those deemed the most dangerous.
At least 14 of the 43 territorial police forces in England and Wales are now using lie detectors, with 14 police officers and 11 staff qualified as polygraph examiners, according to figures obtained by Liberty Investigates.
The data shows 671 polygraph tests were carried out by the 13 forces who provided figures by calendar year, up from 458 in 2018, and a five-year high.
More forces are expected to start using the technology as the College of Policing makes available training through its “polygraph school”.
Polygraph tester Don Cargill reviews Henry’s results
Suspects facing lie detector tests
Testing is “only mandatory by way of conditional caution or a positive obligation of a Sexual Harm Prevention Order or Sexual Risk Order” imposed by the courts, says the National Police Chiefs’ Council, and “any police use of polygraph will form part of a wider and detailed risk management plan tailored to the individual concerned”.
But the University of Northumbria researchers say a non-statutory regime of testing is being carried out by some forces, including on suspects during criminal investigation.
People arrested on suspicion of committing online child sex offences, for example, could be asked to take a test as part of a risk assessment to determine whether they can have contact with children, including their own.
Figures obtained by Prof Oswald and Dr Kotsoglou, using freedom of information requests, show that at least 228 such polygraph interviews were carried out over six years.
Other responses indicated use in “voluntary” risk assessments of convicted sex offenders, including those who apply for removal from the sex offenders’ register, and ambitions to use polygraph testing for more general offences such as violence.
Prof Oswald says: “I think our concern is that should we really in this country be basing really serious criminal justice decisions in a legal system on a scientific technique that is highly contested, to put it mildly, and hasn’t, especially in the policing circumstance, been discussed by parliament?”
The College of Policing says: “The College is working closely with the NPCC to establish a Polygraph School so that policing in England and Wales has access to standardised learning and development in the use of the tool that is tailored to their operating environment.
“The College will develop operational advice so that forces using the tool have a consistent basis on which to do so whilst recognising the relevant legal provisions.”
A new test known as ‘polygraph in a box’ has been developed
What is the future for lie detectors?
The technology has existed in some form for around a century and now Mr Cargill has invented what he calls a “completely revolutionary” Validated Automated Screening Technology (VAST) system – or “polygraph in a box”.
Programmed to find out anything from whether someone has massaged the qualifications on their CV to if they’re a member of an international terrorist organisation, he says the device is as accurate as any polygraph examiner and is already being used by police in the UK.
But the testing time is reduced to around 20 minutes from three hours and can be used with just 15 minutes training.
After filling out a questionnaire, the subject – attached to the device, wearing headphones and sensors on their fingers and palm – is instructed to silently answer “no” to the questions by a person in a recorded video on the screen. A human then grills them about any responses that indicate deception.
“I call it a truth verifier rather than a lie detector because what it’s doing is testing integrity,” explains Mr Cargill.
The technology, he says, would be ideal for use in police vetting and he wants to see it rolled out to areas such as Border Force, where officers could verify someone’s age or country of origin.
UK
Upcoming budget will be big – and Starmer has some serious convincing to do as he fights for survival
Wednesday’s budget is going to be big.
It will be big in terms of tax rises, big in terms of setting the course of the economy and public services, and big in terms of political jeopardy for this government.
The chancellor has a lot of different groups to try to assuage and a lot is at stake.
“There are lots of different audiences to this budget,” says one senior Labour figure. “The markets will be watching, the public on the cost of living, the party on child poverty and business will want to like the direction in which we are travelling – from what I’ve seen so far, it’s a pretty good package.”
The three core principles underpinning the chancellor’s decisions will be to cut NHS waiting lists, cut national debt and cut the cost of living. There will be no return to austerity and no more increases in government borrowing.
Politics Live: Reeves’s ‘mansplaining’ claims are just a ‘smokescreen’, says shadow chancellor
What flows from that is more investment in the NHS, already the big winner in the 2024 Budget, and tax rises to keep funding public services and help plug gaps in the government’s finances.
Some of these gaps are beyond Rachel Reeves’ control, such as the decision by the independent fiscal watchdog (the Office for Budget Responsibility) to downgrade the UK’s productivity forecasts – leaving the chancellor with a £20bn gap in the public finances – or the effect of Donald Trump’s tariffs on the global economy.
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Will PM keep his word on taxes?
Others are self-inflicted, with the chancellor having to find about £7bn to plug her reversals on winter fuel allowance and welfare cuts.
By not pulling the borrowing lever, she hopes to send a message to the markets about stability, and that should help keep down inflation and borrowing costs low, which in turn helps with the cost of living, because inflation and interest rates feed into what we pay for food, for energy, rent and mortgage costs.
That’s what the government is trying to do, but what about the reality when this budget hits?
This is going to be another big Labour budget, where people will be taxed more and the government will spend more.
Only a year ago the chancellor raised a whopping £40bn in taxes and said she wasn’t coming back for more. Now she’s looking to raise more than £30bn.
That the prime minister refused to recommit to his manifesto promise not to raise income tax, VAT or national insurance on working people at the G20 in South Africa days ahead of the budget is instructive: this week we could see the government announce manifesto-breaking tax rises that will leave millions paying more.
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Starmer’s G20 visit overshadowed by Ukraine and budget
Freeze to income thresholds expected
The biggest tax lever, raising income tax rates, was going to be pulled but has now been put back in neutral after the official forecasts came in slightly better than expected, and Downing Street thought again about being the first government in 50 years to raise the income tax rate.
On the one hand, this measure would have been a very clean and clear way of raising £20bn of tax. On the other, there was a view from some in government that the PM and his chancellor would never recover from such a clear breach of trust, with a fair few MPs comparing it to the tuition fees U-turn that torpedoed Nick Clegg’s Lib Dems in the 2015 general election.
Instead, the biggest revenue raiser in the budget will be another two-year freeze on income tax thresholds until 2030.
This is the very thing that Reeves promised she would not do at the last budget in 2024 because “freezing the thresholds will hurt working people” and “take more money out of their payslips”. This week, those words will come back to haunt the chancellor.
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Will this budget help lower your energy bills?
Two-child cap big headline grabber
There will also be more spending and the biggest headline grabber will be the decision to lift the two-child benefit cap.
This was something the PM refused to commit to in the Labour manifesto, because it was one of the things he said he couldn’t afford to do if he wanted to keep taxes low for working people.
But on Wednesday, the government will announce it’s spending £3bn-a-year to lift that cap. Labour MPs will like it, polling suggests the public will not.
What we are going to get on Wednesday is another big tax and spend Labour budget on top of the last.
For the Conservatives, it draws clear dividing lines to take Labour on. They will argue that this is the “same old Labour”, taxing more to spend more, and more with no cuts to public spending.
Having retreated on welfare savings in the summer, to then add more to the welfare bill by lifting the two-child cap is a gift for Labour’s opponents and they will hammer the party on the size of the benefits bill, where the cost of supporting people with long-term health conditions is set to rise from £65bn-a-year to a staggering £100bn by 2029-30.
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Why has chancellor U-turned on income tax rises?
Mansion tax on the cards
There is also a real risk of blow-up in this budget as the chancellor unveils a raft of revenue measures to find that £30bn.
There could be a mansion tax for those living in more expensive homes, a gambling tax, a tourism tax, a milkshake tax.
Ministers are fearful that one of these more modest revenue-raising measures becomes politically massive and blows up.
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This is what happened to George Osborne in 2012 when he announced plans to put 20% of VAT on hot food sold in bakeries and supermarkets. The plan quickly became an attack on the working man’s lunch from out-of-touch Tories and the “pasty tax” was ditched two months later.
And what about the voters? Big tax and spend budgets are the opposite of what Sir Keir Starmer promised the country when he was seeking election. His administration was not going to be another Labour tax and spend government but instead invest in infrastructure to turbocharge growth to help pay for better services and improve people’s everyday lives.
Seventeen months in, the government doesn’t seem to be doing things differently. A year ago, it embarked on the biggest tax-raising budget in a generation, and this week, it goes back on its word and lifts taxes for working people. It creates a big trust deficit.
Pic: PA
Government attempts to tell a better story
There are those in Labour who will read this and point to worse-than-expected government finances, global headwinds and the productivity downgrades as reasons for tax raising.
But it is true too that economists had argued in the run-up to the election that Labour’s position on not cutting spending or raising taxes was unsustainable when you looked at the public finances. Labour took a gamble by saying tax rises were not needed before the election and another one when the chancellor said last year she was not coming back for more.
After a year-and-a-half of governing, the country isn’t feeling better off, the cost of living isn’t easing, the economy isn’t firing, the small boats haven’t been stopped, and the junior doctors are again on strike.
Read more:
Reeves hints at more welfare cuts
Reeves vows to ‘grip the cost of living’
What tax rises could chancellor announce?
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Budget jargon explained
The PM told me at the G7 summit in Canada in June that one of his regrets of his first year wasn’t “we haven’t always told our story as well as we should”.
What you will hear this week is the government trying to better tell that story about what it has achieved to improve people’s lives – be that school breakfast clubs or extending free childcare, increasing the national living wage, giving millions of public sector workers above-inflation pay rises.
You will also hear more about the NHS, as the waiting lists for people in need of non-urgent care within 18 weeks remain stubbornly high. It stood at 7.6m in July 2024 and was at 7.4m at the end of September. The government will talk on Wednesday about how it intends to drive those waits down.
But there is another story from the last 18 months too: Labour said the last budget was a “once in a parliament” tax-raising moment, now it’s coming back for more. Labour said in the election it would protect working people and couldn’t afford to lift the two child-benefit cap, and this week could see both those promises broken.
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Can the Tories be blamed for the financial black hole?
Can PM convince his MPs?
Labour flip-flopped on winter fuel allowance and on benefit cuts, and is now raising your taxes.
Downing Street has been in a constant state of flux as the PM keeps changing his top team, the deputy prime minister had to resign for underpaying her tax, while the UK’s ambassador to the US, Peter Mandelson, was sacked over his ties to the Jeffrey Epstein, the late convicted paedophile. It doesn’t seem much like politics being done differently.
All of the above is why this budget is big. Because Wednesday is not just about the tax and spend measures, big as they may be. It is also about this government, this prime minister, this chancellor. Starmer said ahead of this budget that he was “optimistic” and “if we get this right, our country has a great future”.
But he has some serious convincing to do. Many of his own MPs and those millions of people who voted Labour in, have lost confidence in their ability to deliver, which is why the drumbeat of leadership change now bangs. Going into Wednesday, it’s difficult to imagine how this second tax-raising budget will lessen that noise around a leader and a Labour government that, at the moment, is fighting to survive.
In the upstairs bar of a slick new brewery, the cheese-lovers of Halifax are paying “homage to fromage”.
It is one of the first events in the historic West Yorkshire town for the monthly cheese club and there is a decent turn-out.
Sky News visited Halifax’s clubs, bars and restaurants to get an insight into people’s priorities
The night-time economy in Halifax is a useful measure of how the landscapes of our town and cities have changed
Discussion of Wednesday’s budget is not as popular as an accompaniment to the cheese as the selection of wines. But no one holds back on what is required of the chancellor.
Natalie Rogers, who runs her own small business with her partner, said there needs to be focus.
Small business owner Natalie Rogers wants to see more investment in local industries
“I think investing in small businesses, investing in these northern towns, where at one time we were making all the money for the country, can we not get back to that? We’re not investing in local industries.”
At the next table, with a group of friends, Ali Fletcher said there needs to be bigger targets.
“I think wealth inequality is a major problem. The divide is getting wider. For me, a wealth tax is absolutely critical. We need to address this question of ‘Is there any money left?’. There’s plenty of money, it’s all about choices that government make.”
At this monthly cheese club, people told us about their priorities ahead of the budget
The evening’s cheese tasting was being marshalled by Lisa Kempster. “The impression I get from talking to people is there’s a lot of uncertainty, but when you ask them what they’re uncertain about, they’re not really sure, there’s just a general feeling of uncertainty and being cautious.”
Ali Fletcher reckons wealth inequality is a major problem
Read more:
Budget will be big – and Starmer has some serious convincing to do
Reeves vows to ‘grip the cost of living’
What tax rises could chancellor announce?
This corner of Halifax, close to the town’s historic Piece Hall, is buzzing with clubs, bars and restaurants, trying hard to defy the crunch in the night-time economy. It is a useful measure of how the landscapes of our town and cities has changed.
“Whenever there’s a budget, for a few days afterwards, there’s a drop off in trade,” said Michael Ainsworth, owner of the Graystone Unity, a bar and music venue in the town.
“I accept the government needs to raise money but, in this day and age, there’s better ways to go about doing that, like closing tax loopholes for the huge businesses to operate up with banking arrangements outside the UK.”
Michael Ainsworth owns a bar and music venue and thinks the chancellor needs to close tax loopholes
In the bar, a folk singer is going through a quirky and caustic set. In the basement, a punk band called Edward Molby is considerably louder.
On a sofa in the main bar, recent graduates Josh Kinsella and Ruby Firth, newly arrived in Halifax because of its more affordable housing, pinpoint what they want on Wednesday.
“Can we stop triple-locking the pensions, please? Stop giving pensioners everything. For God’s sake, I know they have hard times in the 70s and the 80s, but it just feels like we’re now paying for everyone else.”
Josh Kinsella and Ruby Firth feel there’s too much focus on pensioners
Ben Randm is a familiar face at the bar and well known on the music scene with his band, Silver Tongued Rascals.
“Everyday people are seen as statistics, we’re always the afterthought. When the cuts are done, we’re always impeded and the ramifications that has for people’s livelihoods, for people’s mental health, for people’s passion and drive… it’s such a struggle.”
He, like many in the night-time economy sector, wants extra help for hospitality and venues that, he says, provide a vital community link.
Ben Randm who has his own band reckons everyday people are ‘always the afterthought’
David Van Gestel chose Halifax to open the third branch of MAMIL, a bar in jokey honour of those cycling “middle-aged men in Lycra”. On a busy quiz night, he said venues had to provide something different to get people out of their homes.
“I think the government needs to start putting some initiatives in place. They talk about growth but the reality is that the only thing we’re seeing grow is our costs.”
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