Tell-Tale Fingerprints

Auckland Star, Volume LXXI, Issue 153, 29 June 1940, Page 4 (Supplement)

Tell-Tale Fingerprints

By--F. Reeder

ORDINARILY, the development of fingerprints to make them clear enough to be photographed is not very difficult. In England prints on dark surfaces are dusted with what is called "grey powder," a mixture of mercury and chalk, and those on light _ surfaces with powdered graphite. In France red lead is used on light surfaces and white lead carbonate on dark surfaces. The powder clings to the oil that has been transferred to the surface from the ridges on the fingers. When prints are suspected on surfaces that do not "take" them well, other means can be used. The use of the vapour of heated iodine is a very delicate method, the fingerprint appearing yellow; its only drawback is that the print is rather difficult to photograph. Fingerprint* three years old have, however, been satisfactorily developed by this means. Delicate Method* Only slightly legs delicate a method is that invented by Dr. worth Mitchell for developing fingerprints on paper. He held the paper over boiling osmium tetroxide, which produced good black prints, full of minute detail. For recording the prints of criminals, the fingers are commonly smeared with printing ink and preestJ on the registration card, but a more delicate method, devised by a French criminologist, Beclere, is to rub the fingerprints with I -powered carbonate of bismuth and the., take a radiograph. This shows up the pores very clearly, a virtue important in the finer applications of fingerprint work, as we shall see. Occasionally, none of the accepted methods of developing fingerprints will serve, and new ones have to be devised, art in a very interesting case that happened in Belgium in 1905, when the Belgian police intercepted a letter believed to have been written by a particularly dangerous anarchist to a fellow conspirator, and asked their chemical expert, M. Jorissen, to confirm their suspicions. By micro-chemical examination, the investigator identified a number of yellow stains on the paper as being potassium ferrocyanide, and treated them with a solution of iron chloride, producing an intense blue colour. *4ruis revealed the stains as fingerprints. Experiments were then carried out to ascertain if possible whether the paper had been impregnated with potassium ferrocyanide before the prints were made, or whether they were made by fingers wet with the chemical. The two alternatives were tried in the laboratory, with pieces of paper similar to the one under examination, and it was found that fingers wet with potas- ! <&

sium ferrocyanide gave prints more like those on the letter than were produced when the fingers were pressed on a piece of paper that had h en soaked in the chemical and then dried. The next problem was to photograph the prints, a difficult one, since blue photographs badly. The prints were darkened by the use of the vapour of ammonium sulphide, and, though the colouration was fugitive, it lasted long enough for six photographs of the prints to be taken. Although they were by no means perfect, they showed sufficient detail for the police to establish twenty points of resemblance with those of the suspected author, who, when arrested and confronted with the evidence, admitted writing the letter when his hands were damp with potassium ferrocyanide that lie was using in the manufacture of a bomb. Gloves do not always safeguard the criminal from leaving his fingerprints behind. When thin gloves are worn over ver; greasy or sweaty fingers, the prints may still pass through. Such occasions are rare, but various wrong-doers who thought that by wearing gloves they had insured themselves against detection, have been victims of this phenomenon. The suggestion that in such cases the fingerprints were forged was disposed of in 1912 by the eminent criminologist Stockis, who found that when he inked his finger in the ordinary way for taking a print, the print could be impressed even through thin rubber or skin gloves. Printed Through Glove A striking instance was recorded in 1919, when a burglary in the Rue Bat d'Argent, in Lyons, was investigated. When fingerprints on a piece of glass from a broken window were developed with lead carbonate,, the impression of a thin woollen material showed up, but through this the fingerprints were sufficiently clear to be identified at the Bureau of Identification as "those of Maurice Reynaud, a known criminal. Reynaud had left for Paris, but a telegram to the Surete arranged for a couple of detectives to be waiting for him at the Gare de Lyon. The stolen property was in his pockets. After his taking the precaution to wear gloves, such an ending must have shocked M. Reynaud profoundly. The explanation was that under siutable conditions the fatty acids exuded by the skin will pass through thin materials, though it is only modern methods of developing and examining fingerprints that have made it possible to examine such faint impressions as are made under these conditions. Other than by wearing gloves, criminals have gone to all sorts of pains

to combat the fingerprint expert. They have sandpapered their fingertips, burned them with acids, even peeled the skin off. But the prints are unalterable. As they are in the baby, so they will be when the baby » a nonagenarian, reappearing unaltered unless the skin and underlying tissues are so deeply damaged that the prints are marred by a scar. Even the Pores "Talk" To Dr. Edmond Locard belongs the credit of a further refinement and extension of fingerprint science. In highly enlarged photographs of good, clear prints, the sweat pores, microscopic openings lying along the tops of the ridges, appear as dots. These vary in number and position in different people's prints. In a good print, these are confirmatory evidence, but in a fragmentary one, they may be the only means of identification. Moreover, prints of the hand, not showing the fingers, may be identified by comparing the number of pores in a particular area with the number in the corresponding area of the suspect's hand. A print as small as a square millimetre would show sufficient pore marks, it is claimed, to be identifiable. This method was first used in Lyons, in 1012, when Dr. Locard obtained the conviction of two burglars, Boudet and Simonin. He had the fingerprints also, but used the pore count to confirm the identification. Both men were arrested on suspicion, Boudet being an old offender, whose fingerprints were easily recognisable on a polished box. Simonin was one of his associates, and was arrested on suspicion, which turned to certainty when his prints were also found on the box. Convictions Seemed At the trial, J)r. JL/ocard showed the jury that nine hundred and one pores could be counted in one of the prints on the box, and the same number in the print of Simonin's corresponding finger. The print of the palm of a hand on the box showed no fewer than two thousand points of similarity, in the distribution of the pores, with the print of Simonin's palm. This was of the utmost importance, for the prints of parts of the hand other than the fingers are often found on the scene of a crime, where no fingerprints sufficiently clear for identification can be obtained. The ridges on the palm of the hand are not sufficiently characteristic to be identified, but the number and distribution of the pores are incontrovertible evidence of identification. Such evidence was accepted from Dr. Locard in a subsequent Lyons case, when a burglar who broke into a cafe, helping himself to a bottle of wine, took the precaution of wrapping a towel round it, but left, all the same, the print of part of his hand. He was convicted on Dr. Locard's identification by pore count. A.