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.
Image: 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.
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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.
Image: 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.
Image: 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.
Image: 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?”
Image: 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.
Image: 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”.
Image: 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.
History of the lie detector
The polygraph machine was invented in 1921 by police officer John Larson in Berkley, California, and has been used by US law enforcement agencies ever since and spread across the world.
His work was picked up by Leonard Keeler, who is widely credited as the inventor of the modern lie detector.
In the 1990s, the polygraph entered the computer age as statisticians at Johns Hopkins University developed an algorithm to analyse the data collected.
Jack Ruby, who shot dead Lee Harvey Oswald two days after he assassinated John F Kennedy requested and was granted a polygraph test to try to prove he was not involved in a conspiracy with Oswald – but then FBI-director J Edgar Hoover said the technique was not “sufficiently precise” to judge truth or deception “without qualification”.
Notable failures include CIA agent Aldrich Ames, who passed two polygraph tests while spying for the Soviet Union.
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.”
Image: 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.
Heathrow Airport bosses had been warned of a potential substation failures less than a week before a major power outage closed the airport for a day, a committee of MPs has heard.
The chief executive of Heathrow Airline Operators’ Committee Nigel Wicking told MPs of the Transport Committee he raised issues about resilience on 15 March after cable and wiring took out lights on a runway.
A fire at an electricity substation in west London meant the power supply was disrupted to Europe’s largest airport for a day – causing travel chaos for around 200,000 passengers.
“I’d actually warned Heathrow of concerns that we had with regard to the substations and my concern was resilience”, Mr Wicking said.
“So the first occasion was to team Heathrow director on the 15th of the month of March. And then I also spoke to the chief operating officer and chief customer officer two days before regarding this concern.
“And it was following a number of, a couple of incidents of, unfortunately, theft, of wire and cable around some of the power supply that on one of those occasions, took out the lights on the runway for a period of time. That obviously made me concerned.”
Mr Wicking also said he believed Heathrow’s Terminal 5 could have been ready to receive repatriation flights by “late morning” on the day of the closure, and that “there was opportunity also to get flights out”.
However, Heathrow chief executive Thomas Woldbye said keeping the airport open during last month’s power outage would have been “disastrous”.
There was a risk of having “literally tens of thousands of people stranded in the airport, where we have nowhere to put them”, Mr Woldbye said.
This breaking news story is being updated and more details will be published shortly.
Another 23 female potential victims have reported that they may have been raped by Zhenhao Zou – the Chinese PhD student detectives believe may be one of the country’s most prolific sex offenders.
The Metropolitan Police launched an international appeal after Zou, 28, was convicted of drugging and raping 10 women following a trial at the Inner London Crown Court last month.
Detectives have not confirmed whether the 23 people who have come forward add to their estimates that more than 50 other women worldwide may have been targeted by the University College London student.
Metropolitan Police commander Kevin Southworth said: “We have victims reaching out to us from different parts of the globe.
“At the moment, the primary places where we believe offending may have occurred at this time appears to be both in England, here in London, and over in China.”
Image: Metropolitan Police commander Kevin Southworth
Zou lived in a student flat in Woburn Place, near Russell Square in central London, and later in a flat in the Uncle building in Churchyard Row in Elephant and Castle, south London.
He had also been a student at Queen’s University Belfast, where he studied mechanical engineering from 2017 until 2019. Police say they have not had any reports from Belfast but added they were “open-minded about that”.
“Given how active and prolific Zou appears to have been with his awful offending, there is every prospect that he could have offended anywhere in the world,” Mr Southworth said.
“We wouldn’t want anyone to write off the fact they may have been a victim of his behaviour simply by virtue of the fact that you are from a certain place.
“The bottom line is, if you think you may have been affected by Zhenhao Zou or someone you know may have been, please don’t hold back. Please make contact with us.”
Image: Pic: Met Police
Zou used hidden or handheld cameras to record his attacks, and kept the footage and often the women’s belongings as souvenirs.
He targeted young, Chinese women, inviting them to his flat for drinks or to study, before drugging and assaulting them.
Zou was convicted of 11 counts of rape, with two of the offences relating to one victim, as well as three counts of voyeurism, 10 counts of possession of an extreme pornographic image, one count of false imprisonment and three counts of possession of a controlled drug with intent to commit a sexual offence, namely butanediol.
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Moment police arrest rapist student
Mr Southworth said: “Of those 10 victims, several were not identified so as we could be sure exactly where in the world they were, but their cases, nevertheless, were sufficient to see convictions at court.
“There were also, at the time, 50 videos that were identified of further potential female victims of Zhenhao Zou’s awful crimes.
“We are still working to identify all of those women in those videos.
“We have now, thankfully, had 23 victim survivors come forward through the appeal that we’ve conducted, some of whom may be identical with some of the females that we saw in those videos, some of whom may even turn out to be from the original indicted cases.”
Mr Southworth added: “Ultimately, now it’s the investigation team’s job to professionally pick our way through those individual pieces of evidence, those individual victims’ stories, to see if we can identify who may have been a victim, when and where, so then we can bring Zou to justice for the full extent of his crimes.”
Mr Southworth said more resources will be put into the investigation, and that detectives are looking to understand “what may have happened without wishing to revisit the trauma, but in a way that enables [the potential victims] to give evidence in the best possible way.”
The Metropolitan Police is appealing to anyone who thinks they may have been targeted by Zou to contact the force either by emailing survivors@met.police.uk, or via the major incident public portal on the force’s website.
An 11-year-old girl who went missing after entering the River Thames has been named as Kaliyah Coa.
An “extensive search” has been carried out after the incident in east London at around 1.30pm on Monday.
Police said the child had been playing during a school inset day and entered the water near Barge House Causeway, North Woolwich.
A recovery mission is now said to be under way to find Kaliyah along the Thames, with the Metropolitan Police carrying out an extensive examination of the area.
Image: Barge House Causeway is a concrete slope in North Woolwich leading into the Thames
Chief Superintendent Dan Card thanked members of the public and emergency teams who responded to “carry out a large-scale search during a highly pressurised and distressing time”.
He also confirmed drone technology and boats were being used to “conduct a thorough search over a wide area”.
He added: “Our specialist officers are supporting Kaliyah’s family through this deeply upsetting time and our thoughts go out to all those impacted by what has happened.”
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“Equally we appreciate this has affected the wider community who have been extremely supportive. You will see extra officers in the area during the coming days.”
On Monday, Kerry Benadjaoud, a 62-year-old resident from the area, said she heard of the incident from her next-door neighbour, who “was outside doing her garden and there was two little kids running, and they said ‘my friend’s in the water'”.
When she arrived at the scene with a life ring, a man told her he had called the police, “but he said at the time he could see her hands going down”.
Barge House Causeway is a concrete slope that goes directly into the River Thames and is used to transport boats.
Residents pointed out that it appeared to be covered in moss and was slippery.