A polygraph expert has outlined how to recognize when someone is lying.
Elizabeth Martin leads Advanced Polygraph.
Advanced Polygraph is the largest polygraph agency in Australia.
She served 22 years with the US police force.
She founded the Advanced Polygraph Corporation in Maryland, USA.
She told the Australian website news.com the classic signs to watch for.
She says people’s “physiology” changes when they lie.
Firstly, small facial signals shift.
These include breathing, the eye blink rate and facial expressions.
Secondly, there are upper and lower body clues.
This covers breathing, feet and leg position, and hand gestures.
Thirdly, a person’s speech alters when they lie.
Ms Martin says: “The tone and pitch of your voice changes and you can get your tenses confused.”
She believes everyone has a “baseline behaviour”.
That is how a person acts when they are being truthful.
When they lie, this baseline behaviour shifts.
She adds: “It’s about learning to read clusters of clues.”
Ms Martin uses polygraphs in her work.
She says polygraphs record the physiological changes in your body when you answer questions.
She described them as devices that “record the physiological changes in your body which occur when you respond to questions.”
The test can return three outcomes: ‘deceptive’, ‘non-deceptive’ or ‘inconclusive’.
Polygraphs are mainly used by law enforcement and intelligence agencies in the USA.
In the UK polygraphs remain controversial.
The machines see little use in the British criminal justice system.
They are perhaps best known for exposing cheating partners on the Jeremy Kyle Show.