On this date in 1806, immigrants Dominic Daley and James Halligan were hanged at Northampton, Massachusetts. In the words of one widely reproduced report, “They persisted in their innocence to the last moment, although there were perhaps not a single one of the numerous spectators present, which was presumed to amount to nearly 15,000, who entertained a doubt of their guilt.” Today, nearly everyone thinks them innocent. The case began, as many wrongful convictions do, with a particularly outrageous crime — a young farmer, Marcus Lyon, found dead in a Massachusetts creek en route to his home in Connecticut. He’d...