A NEW test has been created to catch out people who can trick a normal lie detector.
Researchers at the University of Portsmouth have developed the system which relies on the liar avoiding revealing any guilty information.
For the experiment, 86 people were asked to commit a mock crime by stealing data file in the form of a PDF named "delta" from a computer with a distinct yellow background.
A further 82 people allocated to the control group had no knowledge of the crime.
All of the participants were then subjected to the Symptom Validity Test which requires people to choose one word from a pair of words. Each pair contains a word relating to the crime and a neutral word.
In this experiment, published in Legal and Criminological Psychology, crime-related words included PDF, delta and yellow, and neutral words included JPEG, bravo and red.
In the test, innocent people chose an equal number of crime-related and neutral words. Liars, on the other hand, chose the crime-related words just 33pc of the time and 40pc failed the test after choosing three or fewer crime-related words.
If someone fails the test, it is a strong indication of guilt.