法医学中的指纹-On Fingerprinting within Forensic Science

法医学中的指纹-On Fingerprinting within Forensic Science

Abstract  摘要:

指纹，是我们的脸和手形，指纹，虹膜，脉搏，耳廓等生物特征识别技术中最可靠的因素之一。解释其基本原理和个体识别方法的技术现状，本dissertation针对它进行了研究背景的介绍后，主要集中在分类和其受欢迎的原因，关键的讨论 - 其独特性，稳定性，可访问性和多样性。
     Fingerprint, our face and hand shape, fingerprints, iris, pulse and auricle, has been recognized one of the most dependable factor in Biometric Identification Technology. To plot the rationale and the state of the art of this individual identification method, the present paper, after the description of the background against which it is studied, mainly focuses on the classification and critical discussion about the reasons accounting for its popularity and validity——its uniqueness, stability, accessibility and diversity. Part three aims to describe and explain some of the ways in which fingerprint evidence may be retrieved from a variety of surfaces, in which three ways of identifying latent fingerprints are referred to: optical technology, ultrasonic technology and silicon-based technology. What is also included in part three goes to introduction to some contemporary development in fingerprinting, such as its combination with computer science.

1 Introduction  引言

指纹，作为区分一类人和另一类人最有特色和独特的标记，目前已广泛和专门的在社会活动领域的分类中使用。在进化的基础上，我们可以有把握地认为，其成形发生在婴儿3至4个月大，一个完整的指纹在随之而来的婴儿六个月。几百种图案被认为是对#p#分页标题#e#某个人的定义 - 手指的灯泡。
Fingerprint, as one of the most distinctive and unique mark for distinguishing one from another in human community, now has been widely and exclusively resorted to in an assortment of fields of social activities. On an evolutional basis, we can safely argue that its figuration takes place as early as a baby is three to four months old and a complete formation ensues at babies’ six months. Hundreds of patterns are believed to be found on a certain individual’s defined part ——bulbs of the fingers. Rides and furrows in various forms contribute to the diversity of its patterns, which on the contrary, accounts for its uniqueness. On the other hand, fingerprint is also claimed to be of stability, thus constituting a credible identification-directed tool as the blood type or DNA. It is just the dependence on such diversity, uniqueness and stability that precise validation can be achieved: with fingerprinting, a comparison made between a fingerprint with the preserved ones, we can conduct identification of individuals at ease.
 Fingerprint research has had a long history, according to Lee and Gaensslen (2004: 2): “the earliest evidence of ridge detail on the hands and feet of humans was seen in the 4000-yearold mummies of ancient Egypt”. In modern time, it has been recognized that the first published account of the use of fingerprints as a practical means of identification was the letter written by Dr. Henry Faulds to the British magazine Nature, printed in the October 28, 1880 edition. Nowadays, fingerprinting has come to the stage of rapid development after its combination of computer science and proves to be effective means in the criminal investigation and security-monitoring system. Peripheral products, such as fingerprint access control, lock, safe and remote controller all appear successively to enhance its coverage in information security field to a large extent. The full application of fingerprinting technology in the largest scale is seen in the AFIS (Automated Financial Information System) repository of America operated by the Department of Homeland Security's US Visit Program, containing over 74 million persons’ fingerprints, primarily in the form of two-finger records. Prospective more widespread application in a worldwide sphere is underway.
To outline a general picture of fingerprinting science, which termed as well as Icnophalangometry (Vucetich, 1904 [reported by Locard 1931]), friction ridge skin (Cowger 1983) , lophoscopy (Lambert, 1990) or dactyloscopy (Champod et al, 2004), the present paper, after introducing background and current situation of fingerprinting, mainly dedicates itself to a critical discussion about the reasons why it has been accepted as a unique way of individual identification. Furthermore, in the latter part the variety of surfaces from which evidence may be retrieved is covered, including an introduction to some contemporary developments in this field.#p#分页标题#e#

2 causes for widely-used fingerprinting in identifying individuals  指纹识别个体广泛使用的原因

One may get better informed about the technology of fingerprinting if an acquaintance of some knowledge of dactyloscopy is provided. To describe the pattern forms on the bulks of fingers, researchers established their arguments by referring to the similarity between cross section of a finger and the cross section of a plowed field: “the inside surfaces of the hands from fingertips to wrist and the bottom surfaces of the feet from the tip of the big toe to the rear of the heel contain minute ridges of skin, with furrows between each ridge” (Berry & Stoney, 2004: 1). The ridges and furrows, on the whole, form patterns on the last joint of the fingers and toes, forming four basic types, as shown in Figure 2.1.
#p#分页标题#e#

Figure 2.1 Basic fingerprint patterns (quoted from Berry& David, 2004: 2)
The rationality for the wide application of fingerprinting in establishing the identities of individuals, as mentioned previously, lies in its uniqueness. Fingerprints can be classified into one of the most important categories of physical evidence, which are among the few that can be truly individualized. Fingerprint individuality is widely accepted by scientists and the courts alike. Since the Establishment of the first forensic professional organization, the International Association for Identification (IAI) in 1915, it has been used by the legal authorities to yield accurate discerning of criminals. As far as human and computer comparisons are concerned, no two fingerprints have ever been found alike.
   Compared with other stable human characteristics such as blood type or DNA, fingerprints’ superiority lies in its more convenient and easier accessibility. Another reason why other visible aspects of physical appearance are inferior can be attributed to their changeability. On the contrary, fingerprints do not. In this sense, fingerprints have been rapidly replacing anthropological measurements, thus holding promise for its increasing spread and acceptance worldwide.
     The advantages of fingerprint use now have been well established, however, several negative factors underlying now also challenges its absolute validity from different aspects. The first doubt results from the lack of standardization of fingerprinting and education of fingerprint examiner as well as their raining, leading to the inevitable subjectivity rather than objectivity. Stoney (2004: 5) addressed the problem “finger printing’s insufficiency and incompleteness” by pointing out the three lacking considerations: “(1) the clarity of the ridge detail that is being compared, (2) the finer details that are present in the friction ridge prints, and (3) allowance for differences in  “value” that would account for unusual or special features in the ridge characteristics”. Other problems that complicate the current situation go to the critical technologies within fingerprinting itself and its relevant testing tools. For instance, in the case of criminal discrimination, the decisive means——a fingerprint age estimation remains a subject for further improvement, for at present, “it is generally considered that the determination of the age of a latent finger or palm mark on a particular piece of physical evidence is not possible (Champod et al, 2004: 205)”, there are no presently known scientific tools available for determining the age of a fingerprint deposit. And occasionally, planted or fabricated evidence can completely change police conclusions concerning the scenario of a crime.
      It is clear from what is contained from the paragraphs above that there has been existence of both advantages and disadvantages in fingerprinting. Overally speaking, fingerprinting proves a promising technology in various fields of social activities and deserves to be the last abandonment we are to take. It is not the question whether it is useful and rational or not that we are supposed to invest time and energy on, but rather how a greater utility and practicality can be induced. The core of the whole entity remains to be that fact——to what extent two fingerprints is sufficient to be judged that they were both made by the same finger. To address this issue, two dimensions, i.e. quality and quality determines the amount of correspondence, the former includes how much of the skin surface is represented in the comparison how many (and what kind of) details make up the correspondence; while the latter is determined by how clearly and accurately the skin surface is represented in the two prints (ibid).#p#分页标题#e#

3 Ways to attain fingerprint evidence  实现指纹证据的方式

As far as fingerprints are concerned, they mainly fall into two groups, i.e. visible fingerprints (or patent fingerprints), plastic fingerprints and latent fingerprints. It is the last category of this repertoire that we will endeavor to focus on. To Olsen and Lee (2004), latent fingerprint examiners mostly direct their efforts towards two ultimate goals: enhancement and identification (or elimination) of a latent fingerprint, in other words, the two functions can be termed as validation and distinguishing, of which the former attempts to answer such a question: is he the very person he himself claims to be? While the latter is focused on the question: who he is? Their correlating relationships between fingerprints and functions can be shown in the following figure.

#p#分页标题#e#
.
Figure 3.1 Correlations between fingerprints and functions

Fingerprint identification methods have undergone dramatic changes since it first use by police agencies around the world to identify both suspected criminals as well as the victims of crime in the 19th century. In modern forensic field, fingerprint scientists have been endeavoring to develop new ways or trying to improve the existing methods for the visualization of latent fingerprints, in which the studies on the enhancement of known component of latent fingerprint residue prove to be the most successful. Of all the environmental elements that can induce changes, the method focusing on the surface and corresponding counter measurement remain the best. Champod et al (2004) divide all surfaces bearing latent fingermarks into three groups, porous, semiporous and nonporous. Besides this, changes have been also found to be induced by many other environmental elements. It is no doubt that a complete understanding of all individual components in latent print residue and their quantities has not been achieved, while many of the compounds present are known. The target components include water-soluble substance, lipids. At the countermeasure level, enhancement methods exploit the chemistry of latent residue components and their potential reactions and interactions.
      As for fingerprint identification methods, the earliest evidence can be seen in the application of printing ink in marking. It shortcomings lie in its inaccessibility to the digitalized images, which is obviously improper to be utilized in automated fingerprinting identification. When it comes to the modern time, the retrieval and digitalization mainly resort to fingerprint sensor. Most previous sensors use to be optical and widely exclusively in certain departments such as police stations or banks. Fingers being placed on the optical lenses, ridges in black and furrows in white can be formed on CCD (Charge Coupled Device) after the projection of prism under the built-in light sources. Critically speaking, not a single technology enjoys so long a history and widespread popularity as optically collected fingerprints in the history. However, its defects such as the requirement of sufficiently long optical distance and the induced abnormality caused by too much dryness and greasiness, in addition to its huge cubage, complicate structure all contribute to the limitedness of prospective uses.
    In the late 1990s, technologies based on capacitive effect of semiconductors develop into its maturity. Silicon sensors constitute a plate of the capacitance, in contrast to the other plate—fingers. The difference between the two plates takes its shape with the comparison between the smoothness and the ridges as well as the furrows of the sensor and fingers respectively, i.e. a grey image. Such fingerprint retrieval method is characterized with its image superior to that of optical formation as well as its less reliability and vulnerability to external factors.#p#分页标题#e#
     Considering the deficiency of the previous two methods into account, the urgent need to bring a more advanced substitute involves the ultrasonic technology in. The rationale goes that the position of ridges and furrows can be traced with the difference two resistant forces on skin and on the basis of the penetrating ability of ultrasonic, which can produce kinds of echoes accordingly out of the diversity of materials. Under normal circumstance, the controlled frequency makes guarantee for the safety of humans which protection them from being impaired. In a nutshell, ultrasonic-based fingerprint retrieval method surpasses the former counterparts in its high precision and less demanding cleanliness of fingers as well as the relevant surfaces, in spite of its time-consumingness.    
During past decades, other techniques for discovering latent imprints have sprang up progressively, including the Super Glue (Froude, 1996), laser (Menzel 1999), physical developer (Cantu, 2001), metal deposition (Jones et al, 2001) small particle reagent (Springer & Bergman, 1995) etc. The three stages of fingerprinting, i.e. its retrieval, validation and identification within forensic field have seen thriving developments, foreshadowing the increasing perfect combination of science and technology. Among various retrieval methods, the very core—scanning of certain samples of fingerprint has become a more promising field that leads the direction as a unique forensic subject.
More recently, what deserves our primary attention is the involvement of computer sciences throughout the world, serving the two basic functions——maintaining and searching files of fingerprints. Excellent results can be attained under the condition of computer-aided searches of crime scene imprints. Fingerprint verification algorithm has become a heated subject in information security field, which in turn facilitates the perfection of the technology per se. Sub-questions related to fingerprinting such as the image pretreatment, dichotomy, refinement, retrieval of lines and detailed features as well as its matching all have undergone systematic and standard renovation. They provide more convincing support to the rationality of individual identification. Speedy and accurate scanning and matching are the very characteristics that make it outstand. Though the computers are certainly not 100% efficient, or perhaps the firms who guarantee that their product is literally efficient in this respect are obviously prevaricating for 100% coverage without error will not be possible for some years, while the promising future in this specific field can be the last to be claimed to be outdated.

4 Conclusion  结论

Biometric Identification Technology has developed into an increasingly useful means for individual identification since its first appearance and wide application in the forensic field. The uniqueness is found in our face and hand shape, fingerprints, iris, pulse, auricle and etc. Of all the related indentifying methods in the Biometric Identification Technology market, fingerprinting enjoys the exclusively outstanding popularity out of its uniqueness, stability and accessibility. In addition, the miscellaneous patterns on the ten fingers formed by furrows and ridges contribute to another merit of this——diversity. We argue with full conviction that along its maturing and developmental combinations with advanced industry such as IT technology, it will be bound to open up a wider road for its involvement in forensic science.#p#分页标题#e#
 
References  参考文献:

[1] Berry, J. and Stoney, D.A. (2004), The history and development of fingerprinting, in Advances in Fingerprint Technology, 2nd ed., H.C. Lee and R.E. Gaensslen, Eds., Boca Raton, FL: CRC Press,
[2] Cantu, A.A. (2001), Silver physical developers for the visualization of latent prints on paper, Forensic Sci. Rev., 13, 29–64.
[3] Christophe Champod, Chris Lennard, Pierre Margot and Milutin Stoillovic Fingerprints and Other Ridge Skin Impressions, New York: CRC Press
[4] Cowger, J.F. (1983), Friction Ridge Skin: Comparison and Identification of Fingerprints, New York: Elsevier Science Publishing.
[5] Froude, J.H. (1996), The Super Glue fuming wand: a preliminary evaluation, J. Forensic
[6] Jones, N., Stoilovic, M., Lennard, C.J., and Roux, C. (2001b), Vacuum metal deposition:factors affecting normal and reverse development of latent fingerprints on polyethylene substrates, Forensic Sci. Int., 115, 73–88.75.
[7] Lambert, J.L.F. (1990), International Illustrated Vocabulary of French-English Fingerprint Terminology with a Short Index in Six Languages (Serbian, Japanese, Dutch, Italian,Spanish, German), 2nd ed., Ottawa: Ministry of the Solicitor General, Royal Canadian Mounted Police.
[8] Lee, H. C. and Gaensslen, R. E. (2004). Advances in fingerprint technology. In Fingerprints and Other Ridge Skin Impressions.Christophe Champod, Chris Lennard, Pierre Margot and Milutin Stoillovic Eds. Boca Raton, FL: CRC Press,
[9] Locard, E. (1931), Traité de Criminalistique, Vol. I à VII, Lyon: Joannès Desvigne et Fils Editeurs.
[10] Menzel, E.R. (1999), Fingerprint Detection with Lasers, 2nd ed., New York: Marcel Dekker
[11] Robert D. Olsen, Sr. and Henry C. Lee (2004) Identification of latent prints In Advances in Fingerprint Technology, 2nd ed., H.C. Lee and R.E. Gaensslen, Eds Boca Raton, FL: CRC Press,
[12] Springer, E. and Bergman, P. (1995), A fluorescent small particle reagent (SPR), J. Forensic
Identification, 45, 164–168.
[13] Vucetich, J. (1904), Dactyloscopia Comparada: El Nuevo Sistema Argentino, La Plata, Argentina: Jacobo Peuser.