A British court has convicted James McCormick, 56, for selling fake detectors that did not work and were based on a novelty golf ball finder.
McCormick made an estimated £50m (€58.6m) from sales of his detectors to countries including Iraq, Georgia, and Saudi Arabia.
Prosecutor Richard Whittam said the devices, which sold for up to £27,000 each, claimed to be able to find explosives and drugs under water and from the air.
He told the Old Bailey that in fact they “lacked any grounding in science” and were no better than trying to detect explosives at random.
McCormick of Langport, Somerset, was found guilty of three counts of fraud and will be sentenced on May 2.
The court heard the Advanced Selection Equipment devices had no scientific basis and were based on a £13 American novelty golf ball finder.
McCormick shook his head after the verdicts were delivered.
He is thought to have made about £37m from sales to Iraq alone.
There is no evidence that he tried to sell to the Ministry of Defence, but a ministry inspector watched a demonstration organised by an Essex policeman.
The detectors were marketed to the military, police forces, and governments around the world using glossy brochures and the internet.
Men dressed in military- type fatigues were shown using the detectors to find explosives, drugs, fluids, ivory, and people.
Mr Whittam said fantastic claims were made that the detectors could find substances from planes, under water, under ground, and through walls.
They claimed to be able to bypass “all known forms of concealment” and be able to detect at distance.
Items could be detected up to1km under ground, up to 5km from the air, and 100ft (31m) under water, it was said.
But Mr Whittam added: “The devices did not work and he knew they did not work.
“He had them manufactured so that they could be sold — and despite the fact they did not work, people bought them for a handsome but unwarranted profit.”