IN THE 19th century, Mark Twain played a key role in popularising the then newfangled method of fingerprinting. “Every human being carries with him from his cradle to his grave , and by which he can always be identified – and that without shade of doubt or question,” he wrote.
Until recently, most of us believed that this meant a fingerprint match from a crime scene was proof of guilt. That impression has been cemented by their widespread use, by US immigration services, for instance. But in recent years, several miscarriages of justice…
