  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.
