FINGER-PRINTS AS DETECTIVES.
THE part which science often plays in the detection of crime is a comparatively unimportant, but to many people a peculiarly interesting, chapter of its beneficial story. There is something of the Sherlock Holmes in the composi- tion of the average man,—hence one may deduce the remark- able popularity of Sir A. Conan Doyle's ingenious creation. In the trial of a burglar at the Central Criminal Court last Saturday a part which has no precedent in our Courts was played by one of the finger-prints which Mr. Francis Galton bas done so much to expound to the English student. The burglar in question had made his entry through a window the sill of which happened to have been freshly painted. In doing so he was unlucky enough to leave " a particu- larly plain imprint of his left thumb " on the soft paint. This led to his detection, and the sentence of seven years' penal servitude which the Common Sergeant passed upon him last week. To most people it will not be very clear how this could follow. One thumb, they will say, is very like another; and how can it be said with such certainty that a particular imprint, however clear, belonged to Hemy Jackson rather than to John Smith ? But the truth is that there is no physical characteristic by which a man can be more easily and certainly identified than the print of his thumb. If the reader looks closely at the ball of his thumb, or any of his fingers—wherein a small magnifying glass will be of great assistance—be will see that it is covered with a network of fine lines, arranged in a more or less distinct pattern of arches or loops or whorls. These minute marks are quite distinct from the lines to which the palmist attaches such importance, and though less obvious, they are far better worth study. The lines of cheiromancy, indeed, are the result of use, and indicate the creases into which the skin naturally folds itself when the hands are closed. But the less con- spicuous markings, or "papillary ridges," originate at a much earlier period in the history of the individual, being essential features of the skin itself. They are probably formed by lateral pressure in the skin of the unborn infant their mode of production is thus analogous to that which produces mountain-ranges, as the geologists tell us, by the crumpling which secular shrinkage causes in the earth's crust,—or, to take a more homely illus- tration, to the wrinkles which show themselves on the surface of cooling porridge. It is possible that these ridges are con- nected in some obscure way with our sense of touch, and that we owe to them the power of distinguishing between the various textures of the objects which we handle. What is more important, from the point of view of those who study
crime and its prevention, is that the ridges in question afford a trustworthy means of distinguishing between human beings. They form patterns, as Mr. Galion has pointed out in his brilliant continuation of the work originated by Purkenje eighty years ago, " considerable in size, and of a curious variety of shape, whose boundaries can be firmly outlined, and which are little worlds in themselves. They have the unique merit of retaining all their peculiarities unchanged through- out life, and afford in consequence an incomparably surer criterion of identity than any other bodily feature?'
It may seem at the first glance that the apparently simple markings on the thumb cannot possibly afford such a criterion. Among a number of men the same markings will surely be repeated, so that no reliance can be placed on their evidence. But experience and theory alike show that this is not the case. A great many thousands of thumb-prints made in permanent ink on convenient cards for reference have been examined, and no two alike have yet been discovered. By a calculation which depends on the mathematical laws of probability, and has been purposely "watered down" so far as to be certainly on the safe side, Mr. Galton has shown that there are at least sixty-four thousand million varieties in the arrangement of these lines, any one of which is as likely to occur as any other; in other words, if we assume the number of the human race to be sixteen hundred millions, the chance of any two right or left thumbs presenting the same marks is one in forty. If we take impressions of all ten digits, the chance that two men will be found with the same sets of marks is but one in the tenth power of forty, which is as near a certainty that no two such men will be found as human intelligence can desire. Most juries will convicton less cogent evidence than that. It will be evident that the systematic study of finger-prints is a most valuable aid to the anthropometrist, who busies him- self with the methods of identifying men chiefly in order that habitual criminals may be detected with ease and cer- tainty. Mr. Galton maintains that the system to which he has done so much to call attention is superior in ease of appli- cation and sureness of results to the well- known Bertillon system, which is now in operation in most civilised countries, in spite of the deserved discredit which its inventor drew upon himself when in the Dreyfus case he ventured beyond his own special ground. If a record is made of a criminal's finger-prints when he is first sent to prison, lie can always be identified on his next appearance. Even if be submits to the painful process of destroying his skin with fire or acids, the same tell- tale marks emerge once more when the new skin grows. It is easy to classify and index any number of such records, and it is not surprising that the criminologists of most countries are regarding the finger-print method with increasing favour. Since 1894 it has been in regular use by our own authorities, in conjunction with photography and the Bertillon measure- ments. Of course it is only rarely that finger-prints can actually be used in the detection of crime, and the case already mentioned is the first that one recalls in real life, though a novelist in Chambers's Journal and Mark Twain in "Life on the Mississippi" have shown how murderers might be convicted by the evidence of their blood-stained finger-marks on a damnatory document.
In both East and West, in ancient and modern times, indeed, finger-prints have been put to practical use. India and China. furnish many Instances in which the signature of a deed has been confirmed by the impression of a finger smeared with Indian ink, though it is doubtful how far this was used in the present sense. It has even been suggested that one of the apparently meaningless forms of our law may be traced to a survival of some forgotten anticipation of Mr. Galton's dis- coveries. Laying the finger on a wafer as you remark that you deliver a bond as your act and deed possibly alludes to an ancient practice of leaving a finger-print on the document, just as in some savage tribes a mystic value is attributed to the im- pression of a chief's gory hand on a sacred stone or weapon. The ancient Sovereigns of Japan used to seal State papers with the impression of the Royal hand in vermilion. Bewick, probably acting on his own idea, authenticated some of his books and receipts by an engraved thumb-mark. But the first practical use of thumb-marks as signatures is due to Sir William Herschel, a Bengal Civil servant, who began to use them about 1860 with a view to checking the native taste for forgery and personation. His first idea, borrowed from a native contract on which a thumb-mark was impressed, was to frighten the wily Bengali by attach ing a magical significance to the act, but he speedily noticed the value of the finger-prints as a natural signa- ture that could not possibly be forged. In a land where, as Mr. Kipling observes, a complete murder-case can be pur- chased, including the corpse, for fifty-four rupees, such a check to fraud was most valuable, and Sir William Herschel's experience has been largely utilised by his successors. In 1896 the Postmaster-General of Bengal decided that post- office orders shonld in future be authenticated by the impres- sion of the receiver's thumb. A Hindu has a natural genius for forging a signature, but no amount of study has yet enabled him to adopt the markings on another man's fingers. In this country such a system would happily not be worth the trouble that its introduction would cause ; but there are large possibilities before the study of finger-prints. The whole Tichborne case, for instance, would have fallen to the ground at the outset if the missing Baronet had taken the precaution of leaving an impression of his thumb with his banker, and the easy method of identification which is thus provided must appeal to all who have found by experience the difficulty of persuading foreign authorities, if trouble arises, that they are really the men named on their passports or letters of credit. Forgery, too, would become a lost art if the finger-print were made a compulsory addition to the signature of wills and, other important documents. In that case it would appear that Sydney Smith was really an unconscious prophet when he assured an heraldic inquirer that "the Smiths bad no arms,, but always sealed their letters with their thumbs."
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