DESPITE the effort put into it, and the annoyance caused to innocent travellers, airport security is a pretty haphazard affair. That could change if Ehud Givon has his way. Mr Givon is head of a small Israeli firm called WeCU, which thinks its technology can spot suspicious individuals that traditional methods miss.

WeCU's approach relies on displaying stimuli, such as photographs of individuals who might be known to terrorists but not to ordinary people, or code words that intelligence has discovered are associated with particular operations, and observing what happens. The trick is that the observation is done automatically, and does not rely on the subjective impressions of possibly tired and bored security guards.

When confronted with such stimuli, someone who is unfamiliar with them will merely be bemused and ignore them. Someone who knows what they are, and is feeling guilty about it, will undergo an increase in body temperature, heart rate and breathing rate. WeCU's apparatus is able to monitor the first two of these using an infra-red camera. This captures the heat pattern of blood vessels near the skin, betraying both changes in overall temperature and in heart rate. The system first establishes a baseline for an approaching individual, then flashes the potentially stimulating image on a screen or wall in the subject's eyeline. If the baseline changes in a way that is suspicious, the individual can be ushered away for further questioning.

The beauty of this system is that it does not rely, as traditional “lie detectors” like polygraphs do, on a formal procedure to determine whether an individual is under emotional pressure. That technique has often been shown to be unreliable—producing both false positives (because it puts innocent people under stress) and false negatives (because practised bad guys can keep their emotional responses under control). As Mr Givon points out, the bank of stimuli included in the system is varied and unpredictable. Even a skilled, well practised suspect who is aware of the system and who tries to prepare for the screening cannot know where the stimuli will come from and how they will appear.

The system has been demonstrated to a number of authorities worldwide. Mr Givon says tests with hundreds of subjects in both laboratory and real-life situations have shown that 95% of those flagged up are indeed “persons of interest” with whom the powers that be would like to have a chat. If further tests confirm its advantages, travellers in some airports may soon find themselves looking at unexpected slide-shows when they visit the airport.