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THE Jeremy Kyle Show, which has been broadcast in the UK since 2005, was axed by ITV last week. It featured people with troubled relationships arguing in front of a live audience, often spiced up with the addition of a lie detector test. In an episode filmed recently, but never broadcast, a guest failed such a test designed to find out if he had cheated on his fianc茅e. He was later found dead.

Lie detector tests aren鈥檛 exactly rare on TV. We can thank Kyle鈥檚 US predecessor Jerry Springer for cementing their popularity, and they endure on shows like Love Island, another ITV programme. But their reach goes wider. In Ukraine, evidence from lie detector tests, also known as polygraphs, is admissible in court, while in the US they are used as part of the recruitment process to government jobs.

All this is rather worrying as lie detectors don鈥檛 live up to their name. They have long been discredited, while other methods of finding the truth are gaining ground.

鈥淚t鈥檚 good that the show has ended,鈥� says George Maschke, an based in the Netherlands. He says the programme contributed to the public mistakenly believing that lie detectors work or have any scientific basis. ITV didn鈥檛 respond to questions about its use of lie detectors.

Polygraph machines measure a person鈥檚 pulse, blood pressure and breathing while they answer a series of control questions, like what they ate for breakfast or their age. Then the person is asked a more pertinent question, such as: 鈥淒id you cheat on your partner?鈥� If their vital signs leap, they are judged to be lying.

But this is wrong. The factors being measured are designed to tally with a person鈥檚 level of arousal, which you can think of as how alert they are. Yet being asked whether you were unfaithful is the sort of thing that could make you tense up whether you were or not.

This isn鈥檛 news. In the 1980s, psychologist David Lykken wrote about the lack of evidence that polygraphs could detect lies. He found that several studies claiming they had an accuracy of 70 per cent or more were . A 2003 reached much the same view.

Maschke knows this all too well. In 1995, he applied to work for the FBI as an intelligence officer, but failed a polygraph and was refused. 鈥淚 couldn鈥檛 understand how I had failed until I read everything on polygraphs and discovered that they are nonsense,鈥� he says.

Back in 1959, Lykken , now known as the Concealed Information Test (CIT). This tries to determine not whether a person is lying, but whether they have a memory of information being presented to them.

For instance, the examiner might ask someone: 鈥淲here did the thief hide what he stole? Repeat these possibilities after me. Was it in the bathroom? In the locker? On the coatrack? On the windowsill?鈥� The person鈥檚 skin conductance is measured during these questions. If it spikes during one of them, it suggests that they are sweating more, and that option is meaningful to them.

The test is different to the polygraph because all the options are part of the same overall question. And if a person says they have no knowledge of the crime, but the test indicates they do, you can infer they are probably lying. It has been used for years by police in Japan to help direct enquiries in the early stages of investigations.

Although the CIT rests on solid foundations, it isn鈥檛 a perfect memory detector. A 2014 did uncover a significant statistical difference between the results of people with guilty knowledge and without it. Yet, at best, a person who does have such a memory would be about 90 per cent more likely to get a higher skin conductance reading than someone who doesn鈥檛. That might sound high, but a test with that success rate is likely to produce false negatives: results suggesting that people don鈥檛 have knowledge when they actually do.

Linda Geven, a legal psychologist at the University of Amsterdam in the Netherlands says this shows why the CIT shouldn鈥檛 be relied on in court as the sole proof of guilt. 鈥淵ou would use it more in the investigation stage,鈥� she says. 鈥淔or example, to work out if the police should look at one suspect more closely than the others.鈥�

Even then, what CIT does detect may not always be a relevant 鈥渕emory trace鈥�, as Geven calls them. For example, interviewees might recognise a suspect from news reports, even when they don鈥檛 really know them. She is researching whether asking more specific questions could get around this.

More recently, it has emerged that the CIT may reveal not just whether people have a memory of a detail, but whether they are deliberately covering it up. Nathalie Klein-Selle at the Hebrew University of Jerusalem in Israel has found that, although increased skin conductance does reveal the presence of that memory, heart rate and breathing . This might sound like the polygraph, but it is more reliable because the test aims to avoid inducing stress by only presenting interviewees with plausible answers.

Researchers are also exploring other outward cues that could improve the CIT, including how people鈥檚 eyes move as they look at photos of faces. Psychologist Ailsa Millen at the University of Stirling in the UK has differs when we recognise the face. The effect is stronger for faces we know best, such as close friends.

鈥淚 read everything written about polygraphs and discovered that they are nonsense鈥�

Millen is now working on a project called to develop this test, potentially for use by UK police. But many unknowns must first be resolved, including whether the test works equally well when people from one culture look at faces from another. Millen is currently studying whether people can conceal their recognition of faces.

All of which means there is little excuse for still using polygraphs, whether on TV or elsewhere. For his part, Maschke is campaigning for them to be dropped, like Kyle鈥檚 show itself. 鈥淥ur focus is on public education,鈥� he says. 鈥淔or policy reform to happen, more people have to understand why lie detectors are not reliable.鈥�