James McCormick, 56, was found guilty at the Old Bailey of three counts of fraud after jurors heard that his 27,000 pounds Advanced Detection Equipment devices had no scientific basis, and were modelled on a 13 pound novelty golf ball finder.
McCormick, of Langport, Somerset, made an estimated 50 million pounds, marketing his three models to armies, police forces and governments around the world using glossy brochures and the internet. Two thirds of his sales were to the Iraqi government.
Items could be detected through walls, up to 1 kilometre underground, up to 5 kilometres from the air and 31 metres underwater, it was said.
Sensor cards slotted into the machine were colour-coded - orange for explosives, blue for drugs and red for humans.
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"The devices did not work and he knew they did not work," said Richard Whittam, prosecuting.
"He made them knowing that they were going to be sold as something that it was claimed was simply fantastic. You may think those claims are incredible," Whittam said.
McCormick bought 300 Golfinder machines for finding golf balls from the US between 2005 and 2006, a gadget advertised as a "great novelty item" which used the customer's body to "energise its actions".
"During 2007 the volume of devices required by James McCormick increased. He said this was due to a large contract he had obtained with the Iraqi government," Whittam said.
Experts who assessed the most expensive model, the ADE 651, which was used in Iraq, said it had no grounding in science and was completely ineffectual, he said. It was no better than trying to detect explosives at random.
One of them was even used to check a hotel in Romania before the visit of an American president in the 90s, he said.