Last year, New Scientist revealed that the US Department of Homeland Security is developing a system designed to detect "hostile thoughts" in people walking through border posts, airports and public places. The DHS says recent tests prove it works.
Project Hostile Intent as it was called aimed to help security staff choose who to pull over for a gently probing interview - or more.
Commentators slated the idea that sensors could spot people up to no good from their pulse rate, breathing, skin temperature, or fleeting facial expressions. One likened it to the "pre-crime" units that predict criminal behaviour in the movie Minority Report.
However, last week, the DHS science unit gave an update on the project, now dubbed the less-hostile-sounding Future Attribute Screening Technologies (FAST) programme. And, if DHS claims are to be believed, the research appears to be getting somewhere.
At an equestrian centre in Maryland, 140 paid volunteers walked through a pair of trailers kitted out with a battery of FAST sensors, including cameras, infrared heat sensors and an eyesafe laser radar, called a Bio-Lidar, that measures pulse and breathing rate from a distance.
Some subjects were told to act shifty, be evasive, deceptive and hostile. And many were detected. "We're still very early on in this research, but it is looking very promising," says DHS science spokesman John Verrico. "We are running at about 78% accuracy on mal-intent detection, and 80% on deception."
That sounds incredibly high at such an early stage in the research - but only tests on vast quantities of real people, rather than eager volunteers, will present any real test.
Questions remain, however, as to how secure the system is. The machines could reveal health conditions like heart murmurs and breathing problems as well as stress levels - which would be an invasion of privacy.
But Verrico says FAST has been through stringent privacy controls (pdf) and that the data is never matched to a name. It is only used to make decisions about whether to question someone, and then discarded.
The trial technology was installed in a trailer because it is planned to be easily transportable, so that FAST trucks can appear at any sports or music event as required. They look set to become as regular a sight at such events as mobile toilets and catering trucks.
But is going to make a real difference? Or will bad guys learn to play the system and render it another piece of what expert Bruce Schneier dubs "security theatre".