The 'Babes in the Wood' killer gave away his guilt more than 30 years before his conviction, according to body language, linguistics and psychology experts. See them reveal the telltale signs here:
Nine-year-old friends Karen Haddaway and Nicola Fellows were sexually assaulted and strangled to death in a woodland in Brighton, UK, in 1986 - in what became known as the Babes in the Wood murders.
Russell Bishop, a 20-year-old roofer at the time, was charged with killings but later acquitted in court.
It took more than 30 years and a change in the law, fought for by the girls' families, before Bishop was convicted at a retrial in 2018. However, experts who have analysed old interview footage think his guilt was obvious all along.
In a TV interview following his original trial in 1987, there are clear physiological signs that he is hiding something, according to body language expert Dr Cliff Langley.
Reviewing the footage in series Faking It, he said: "There's an anxiety that's beneath the surface and this is indicated by an increase in blink break.
"That means that he's thinking hard, because blinking, when it increases in rate, is an indication of cognitive load.
"If we also watch his chest, we see an increase in upper chest breathing. Normally, when we're comfortable, we breathe from the stomach. This is why on a polygraph, they have two straps, they have one around the abdomen, and one around the chest. And so they can determine if the breath changes, to the upper chest, which signals anxiety.
"Now, we don't need a polygraph, because we can watch that breathing, from the chest here, with the rise and fall of his clothing. So, combined with rapid blinking and the upper chest breathing, we can be fairly confident that anxiety has increased at this point."
Bishop's choice of language was also quite revealing, according to professor of linguistics Dawn Archer. In particular, his claim that he had 'nothing to hide' suggested quite the opposite.
She explained: "We get a really interesting word choice here because why would you mention something like hiding, nobody is talking about hiding?
"You hide because you've got a reason to hide, and what he's doing is going on record to say that he does not have a reason to hide.
"He's the one who introduces this idea of hiding away, which we associate as a culture with this idea of guilt and shame."
Focusing on patterns in his speech, she continued: "Notice we also get full forms from him at this point - 'They knew all along that I did not do this' instead of 'I didn't do this'.
"We sometimes associate that full form with attempts to deceive, because we're going into convince mode."
Bishop was eventually found guilty of murdering Karen and Nicola 32 years on from the horrific crimes. Describing him as a 'predatory paedophile' who subjected his victims to 'unimaginable terror in their final moments', the judge sentenced Bishop to two life sentences with a minimum term of 36 years.
Forensic psychologist Kerry Daynes said Bishop is the stuff of nightmares.
She said: "He is one of those rare bogeymen-type characters that we warn all children about, and he's definitely the stuff of parents' nightmares.
"He's also one of Britain's longest serving inmates and he'll never have the freedom to offend again."
You can watch Faking It on discovery+.
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