FORENSIC PRACTICE Krystyn Łuszczuk, M.Sc. Eng. IT specialist, member of the Polish Forensic Association Mieczysław Goc, Ph.D. (corresponding author) Professor at the WSB University in Gdańsk, Deputy President of the Polish Forensic Association Andrzej Łuszczuk, M.Sc. Document expert at the Polish Forensic Association Use of scangraphy for computer visualization of handwritten text shading Summary The article indicates the importance of computer programs as tools supporting the handwriting expertise and increasing its objectivity. Some of these programs are based on computer scangraphy. Scangraphy is a handwriting examination method in which a text sample is treated as a raster image (a bitmap), i.e. a set of single (dots) pixels. The bitmap pixel pattern can be tested in a variety of different ways, as required. The article describes the first computer program to use scangraphy in handwriting examination. Key words: scangraphy, handwriting, computer handwriting scans, SCANGRAF Introduction of expert opinions, particularly vivid in the doctrine Studies on handwriting are mainly based on qualitative and American jurisprudence, not always favorable to methods. Quantitative methods, consisting of different the handwriting expertise, often classifying it as the types of measurements, instrumental analyses and so-called non-scientific evidence, has led, on the one statistical calculations, which guarantee high precision hand, to the development of criteria for the admissibility and repeatability of results, have a minor usage. Due to of such evidence in court proceedings2, and, on the limited role of measurements in handwriting expertise, other hand, to the initiation of studies on the actual subjective evaluation of test results by an expert is of state of handwriting expertise, including the relevant key importance1. Such an evaluation is based on the methodology and, above all, to the development of new, expert’s experience, knowledge and qualifications and, more objective test methods, based, among others, on therefore, its results are frequently not as unambiguous computer techniques3. However, this does not mean as in the case of quantitative methods (Moszczyński, that traditional methods of handwriting examination 2011, pp. 126-138). This feature of the handwriting have no scientific basis. Their scientific character has examination was the main argument raised by critics been confirmed both by many years of expert practice of handwriting expertise, who allege that this method and by the opinion of the vast majority of authors of has an inadequate level of metric characteristic scientific publications on this subject4. Undoubtedly, the determinants, is intuitive and subjective with regard to identification. The discussion on the scientific character 2 The most popular are the so called Daubert’s standards. 3 These issues are presented, among others, in the 1 This aspect of the handwriting opinion has been pointed monograph of M. Goc (2016). by many authors, including W.R.Harrison, who, as early as 4 The issues related to the scientific basis of handwriting in the 1950s, wrote that handwriting comparative analyses expertise, together with the criticism of the position which are to a large extent subjective, which exposes them to undermines the possibility of issuing categorical opinions misinterpretations. (Harrison, 1958, p. 342). Cf. also Widła, and the simultaneous indication of the scale and causes 1982, pp. 83–96; Hecker, 2000, p. 193; Kwiatkowska- of errors in handwriting expertises, are comprehensively -Wójcikiewicz, Wójcikiewicz, 2010, pp. 319–328; Mosz- presented in the monograph cited above Goc, 2016, czyński, 2011, pp. 126–138. pp. 47–106). ISSUES OF FORENSIC SCIENCE 300(2) 2018 55 FORENSIC PRACTICE introduction of computer technology in the handwriting Table 1. Handwriting parameters tested by GLOBALGRAF expertise in the last years constitutes an important step package. towards increasing the method’s objectivity. Computer techniques significantly reduce the subjectivity factor, GLOBALGRAF but do not eliminate it completely. The final handwriting identification decision is left to the discretion of the Lp. Program Parameters tested expert, while the task of the computer programs is to Shape coefficient facilitate the expert’s decision. Computer programs facilitating handwriting examination have been 1. GRAPHOTYPE Size ratio used for several years abroad, as well as in Poland. Graphotype A team of experts of the Polish Forensic Association in cooperation with academic staff of the University of Kinetic-Geometric Probability Warsaw and experts of the Central Forensic Laboratory Index 2. KINEGRAF of the Police within the framework of development Identification value of the 5 projects financed by the Ministry of Science and handwriting sample Higher Education (MNiSW) and the National Centre for Research and Development (NCBiR) developed Linearity coefficient two packages of computer applications supporting Angular similarity coefficient handwriting examination. The first package called GLOBALGRAF consists of four computer programs: 3. RAYGRAF Morpheme density factor GRAFOTYP, KINEGRAF, RAYGRAF i SCANGRAF. Letter density coefficient These programs are already being used in expert practice and receive a positive feedback. The second Impulse factor package, GLOBALGRAF II, was completed in 2016 and includes four additional programs: BARWOSKAN, CENTROGRAF, LINIOGRAF and PROFILOSKAN. because this program has nothing to do with These programs use two basic test methods, i.e. graphometry, as it does not measure any parameters, computer graphometry6 and scangraphy7. but is used to visualize the pressure (shading system) in the scripts examined. For this purpose, it uses the Computer graphometry scangraphy method mentioned in the introduction. As the name suggests, graphometry tests the basic, geometric parameters of handwriting, such as lengths, Scangraphy widths, angles of inclination, curvature, surfaces, Scangraphy is the result of a search for a test method densities and impulses. Once tedious and time- that would allow to study and compare the features of consuming (carried out manually on the enlarged handwriting resulting from an uncontrolled writing habit script images), these measurements do not pose any (without the consciousness of the writer) and, at the major problems after the introduction of computer same time, characterized by a relatively high level of techniques. Moreover, computer technology allows individualization and graphokinetic stability. According the implementation of new parameters, which are to handwriting experts, such a feature, difficult to mathematical transformations of basic parameters. imitate, is shading and pressuring of handwriting, where The table below shows the handwriting parameters scangraphy can be the method of choice to facilitate tested by the aforementioned GLOBALGRAF package. comparative analysis of this feature. Scangraphy It is easy to notice that Table 1 lacks the fourth breaks with the traditional perception of handwriting program of the package, namely SCANGRAF. It is from the perspective of its graphicism. A text sample is treated as a bitmap, which undergoes a cyclical transformation revealing the distribution of pressure 5 (cf. Development Project No. OR 00003807 “Development over the surface underneath the writing instrument of methodology and programs and construction of (Łuszczuk, Łuszczuk, 2012, p. 226). a workstation for identification of handwriting and signatures Scangraphy assumes the principle (already verified using computer graphometry” (completed on 8 July 2011) in expert practice) that the phenomenon of “shading” and Development Project No. DOBR-BIO4/038/13297/2013 occurring in a handwritten document is the result of “Measuring tools to support handwriting and signature changing pressure exerted on the surface by a writing analysis” (completed in December 2016). instrument, causing some of the drawn lines to be more, 6 Computer graphometry – a term proposed (A. Łuszczuk, K. Łuszczuk) at the 5th Forensic Seminar in May 2009 in while other to be less saturated, depending on the Ciechocinek. pressure. Scangraphy is a colorimetric method which 7 The test method proposed by A. Łuszczuk and K. Łuszczuk does not test the so-called graphism of handwriting in June 2010 at the 14th Wrocław Symposium for as such, but the colour content of a raster image Handwriting Examination. (a photographed or scanned writing sample). Such 56 ISSUES OF FORENSIC SCIENCE 300(2) 2018 FORENSIC PRACTICE Fig. 1. A – Signature sample, B – Enlarged fragment showing the pixel structure. a digital sample image, composed of single (dots) pixels ranging between 0 (lack of component) and 255 is called a “bitmap”. Each digital image, obtained from (maximum saturation). Figure 2 summarizes some a scanner, a digital camera or a camcorder, represents examples of pixel colour determination according to a collection of such points (pixels), whose number the RGB colour model. depends on the so-called resolution of the recording Scangraphy enables qualitative and quantitative device8 (digital camera, camcorder, scanner, etc.). The analysis of the bitmap’s colour structure. It allows to pixel structure of a digital image becomes visible when test each pixel’s RGB, change the colour values of zooming in. The higher the resolution of the output the components, invert and convert the image, and image, the greater the magnification required to make compare brightness between pixels in the same bitmap