Two of the most outspoken expert witnesses are Wolf Luis Mochan at the National University of Mexico and Alejandro Ramirez-Solis at the Universidad Autonoma del Estado de Morelos, who are both physicists. These scientists say the device is useless and in one trial, carried out double blind experiments to test its efficacy.
The results of these tests were not originally published because they were part of an ongoing trial. But with the court proceedings now over, Mochan and Ramirez-Solis say they are happy to release the paper (although a Mexican newspaper somehow got hold of the results and published them last year). Today, their work appears on the arXiv.
The results are unsurprising. When the solider was aware of the location, the GT200 worked perfectly, identifying the correct box on all four occasions.
But when the soldier was unaware of the location, the GT200 located the contraband on only three occasions out of 20, a result that is entirely compatible with chance.
Here is the paper.
The GT200 is a device that has been extensively used by the Mexican armed forces to remotely detect and identify substances such as drugs and explosives. A double blind experiment has been performed to test its effectivity. In seventeen out of twenty attempts, the GT200 failed in the hands of certified operators to find more than 1600 amphetamine pills and four bullets hidden in a randomly chosen cardboard box out of eight identical boxes distributed within a 90m$\times$20m ballroom. This result is compatible with the 1/8 probability expected for a completely ineffectual device, and is incompatible with even a moderately effective working one.
Here is our previous coverage on the GT200 bomb detector.
Dowsing is an ancient form of divination. Sadly, magic doesn’t work. Neither does dowsing regardless of the endless testimonials of people who say it worked for them. Skeptic Dictionary has the modern take on dowsing.
A modern twist to the ancient art of dowsing has been added by several entrepreneurs who have added a plastic handle to the dowsing rod and either fake or pointless electronic circuitry. These devices are not marketed as dowsing rods, but as machines capable of detecting drugs, bombs, or a variety of other things.
And the GT200
Although the GT 200 is nothing more than a divining rod, Mexican defense officials praise the devices as a critical part of their efforts to combat drug traffickers. In November, 2009, at a checkpoint on the highway leading from Mexico City to Monterrey, the device pointed at a Volkswagen containing a man, a woman, and a child. Soldiers surrounded the vehicle and a search was conducted for illegal drugs. But all they found was a bottle of Tylenol — evidence, the soldier operating the device said, of how sensitive the GT 200 was.
Tip: Matt Crowley