Sir

Your News report on the fake fingerprints made by mathematician Tsutomu Matsumoto, using gelatin and a plastic mould (Nature 417, 676; 200210.1038/417676b), is interesting, but hardly novel. An analogous but more elegant technique was described by the great British mystery writer R. Austin Freeman in The Red Thumb Mark, first published by Collingwood Brothers, London, in 1907.

In the book, Freeman, in the guise of his scientific detective Dr Thorndyke, explained how regions of a plate of “chromicized gelatine” exposed to light under a negative image of a fingerprint would be inversely soluble in hot water, according to how much light each area received. Gelatin under the fingerprint ridges would receive more light and would be preserved when the plate was rinsed with hot water. A three-dimensional gelatin replica of a fingerprint would result.

“The process that I have described,” said Thorndyke, “is, in all essentials, that which is used in the reproduction of pen-and-ink drawings, and any of the hundreds of workmen who are employed in that industry could make a relief block of a finger-print with which an undetectable forgery could be executed.” I have no doubt that Freeman's gelatin fingerprint could fool an optical scanner as well as Matsumoto's.

Many more details are provided in The Red Thumb Mark, which mystery buffs among Nature's readers will doubtless enjoy — even though I have given away part of the ending. This is one of several Dr Thorndyke stories that have recently been reprinted (Stratus, London, 2001).