In the spring of 1696, Isaac Newton left Cambridge for the Tower of London to take up what had long been a quiet sinecure: Warden of the Royal Mint. He arrived into a currency falling apart. England's silver coin had been shaved and clipped for so long that it had lost about half its legal weight. Newton's job was to recoin the country's money and run down the counterfeiters profiting from the confusion. The most accomplished of them was William Chaloner.
Chaloner had learned to counterfeit from a goldsmith, Patrick Coffee, and commissioned the dies he needed from an engraver, Thomas Taylor. By his own later admission he ran up some thirty thousand pounds in fake currency within a decade: French gold pistoles first, then English guineas, crowns, and half-crowns, struck from commissioned dies. Newton's file on him traces him, within seven years, from a threadbare, dye-stained tradesman to a gentleman with a house in Knightsbridge and plate on his table. He had escaped prosecution before, each time before a case against him could be made to hold.
What finally caught him looks, from a distance, like patient evidence defeating a practiced liar. For months Newton collected and cross-checked depositions from Chaloner's own former partners, building a record reaching back to 1690. Among several charges brought in March 1699 was one oddly specific count: that in a single day, Chaloner had struck more than a hundred coins, gold and silver, in six different denominations. None of Newton's six trial witnesses proved that count directly. Four spoke instead to other crimes from years earlier, some separately charged and some not; only two testified to the spree itself, swearing they had seen Chaloner make shillings on the date in the indictment, testimony the historian Thomas Levenson judges almost certainly false in its particulars. The jury convicted him anyway, in minutes.
Chaloner's own defense pointed at exactly this gap. No one, he told Newton from Newgate, had sworn to seeing him actually strike a coin; the date on the indictment could not be proved against him; and no precedent existed, he wrote, for convicting a man of coining on bare testimony without circumstances to corroborate it. That same standard had freed him once already, in 1695, when a coining accusation against him went nowhere for lack of anything beyond one man's word. This time it did him no good. Sentenced the next day, Chaloner wrote to Newton, begging to be spared. Newton did not reply. He was hanged at Tyburn on March 22, 1699.
On the fuller record, Chaloner was guilty many times over, and Newton's own work had established that beyond doubt. Whether the spree he was convicted of actually happened is a different question, since the only testimony that spoke to it directly is testimony a historian doubts, and the two are easy to confuse: a correct verdict feels like proof that everything behind it was sound. Newton spent his scientific life refusing to let a plausible story stand in for a demonstrated one. Prosecuting Chaloner, the court let the weight of years of other crimes substitute for proof of the spree it had charged him with. The coin was counterfeit. So, it seems, was the specific charge that hanged the man who made it.