Sir

While surveying the history of fingerprinting at the National Archives of India in New Delhi, we came across an early reference to forged fingerprints, similar to that described in your fascinating News item “Detectors licked by gummy fingers” (Nature 417, 676; 200210.1038/417676b, and see D. Ehrenfeld, Nature 418, 583; 200210.1038/418583a).

In 1917, when the science of fingerprinting was in its infancy, news of a demonstration by a lawyer in a court in Howrah (Bengal, India) threatened to undermine the value of this discipline (Home Department Proceedings 202–206 (A), Police Branch, Government of India, August 1919).

The lawyer, Babu Panchkowry Chatterji, was then invited to Bengal Fingerprint Bureau and asked to re-demonstrate his experiment. He took a thin piece of paper and smeared it lightly with gum arabic. He then placed it over a fingermark and pressed it for one to two minutes. Next, he slightly wetted the paper and separated it from the original impression so that it now carried the negative of the imprint. He applied the negative to a fresh sample of paper, wetted and pressed it again, and removed it, thus producing a clear replica of the original impression. The original fingermark was not damaged by this process.

These findings made sensational news. It was feared that astute money lenders would implant borrowers' thumbprints on fresh proforma and fill in larger amounts and/or higher rates of interest. When the case was referred to F. Brewester, the then Government Examiner of Questioned Documents, he submitted himself to a test prepared by Howrah Bar. The test consisted of 12 fingerprints — a random mix of genuine and transferred ones — on a single sheet of paper. He was asked to segregate them. In one attempt, Brewester identified the forged fingerprints. He noticed three differences: the transferred prints had diffuse lines while the originals had sharp patterns; the transferred prints were impregnated with gum; and the fibres on the part of the paper with transferred prints were disoriented.

Brewester therefore concluded that an observant fingerprint expert can easily differentiate an original mark from a transplanted one.