Rapid and non-destructive approach for characterization and differentiation of sealing wax using ATR-FTIR spectroscopy

Sealing wax is used for maintaining the integrity and authenticity of a document or physical evidence. Any tampering with the seal calls into question the overall integrity and authenticity of the tangible evidence or document. In these circumstances, determining the authenticity of the sealing material (physical and chemical) becomes imperative. In this study, ATR-FTIR spectroscopy supported by chemometrics has been used to differentiate sealing wax samples belonging to 12 different brands available across India. All the samples were first melted, cooled, and then analyzed using ATR-FTIR spectroscopy in the mid-infrared region (4000-600 cm-1 ). The obtained spectra were first examined visually for the presence of different functional groups. Principal component analysis (PCA) and principal component analysis-linear discriminant analysis (PCA-LDA) were employed to analyze the sample clustering patterns and to categorize them into their respective groups, respectively. For classification, a PCA-LDA training model was applied, and it demonstrated 95.83% accuracy. The validation test resulted in an accuracy of 83.33%. PCA-LDA model offered 100% accurate prediction for samples on various substrates, including cloth, cardboard, and paper. A blind study was also performed using five unknown samples, which were accurately classified into their respective groups. PCA-LDA model will be helpful in providing investigative leads by linking a questioned sealing wax sample with its respective group.

Structural and optical characterization of banknotes using spectral-domain optical coherence tomography

Counterfeiting of banknotes remains a severe threat to economic security and social stability. The characterization of banknote has mainly relied on the assessment of various security features applied to the surface of the note. However, the surface features are easy to forge and contain insufficient information to discover the source. In this paper, a novel approach for banknote characterization has been proposed by employing spectral-domain optical coherence tomography (SD-OCT) that can provide structural and optical features. Three groups of counterfeit Chinese 100 Yuan banknotes produced by different printing manners and one group of authentic banknotes were examined by SD-OCT without any sample preparation and four distinct areas were selected for imaging. High-resolution tomographic and three-dimensional (3D) volumetric OCT images were obtained and a set of features were first revealed to characterize the banknotes qualitatively and quantitatively. The results demonstrated that SD-OCT was effective to detect and classify different types of counterfeit banknotes and could potentially be used to link counterfeit banknotes to their sources in a fast, simple and nondestructive manner.

Top interpretable neural network for handwriting identification

Machine learning (ML) has become one of the most promising tools in forensics, despite its dominant method of artificial neural networks (ANNs) suffering from the black-box problem. While forensic methodology demands explainability and evaluativity, neural networks are unexplainable, hence almost unfalsifiable. Our study was conducted to mitigate this problem in a case-like context, by creating a novel top interpretable neural network (TINN) for identification of the authors of handwritten documents. The idea of top interpretability assumes that it is irrelevant how the handwriting features are extracted from documents, as long as they are semantically sensible and the sole determinants of identification. The model was tasked with supervised extraction of handwriting characteristics and subsequent identification of the writers on that basis. The interpretable model not only outperformed all comparative models in terms of author identification, but also underperformed in terms of features extraction (achieving satisfactory results nonetheless). Visualizations of features-extracted by the model to perform its tasks-suggest that it considers rational and semantically sensible features of handwriting, but we are unable to determine whether it learned the exact features of handwriting we desired. The approach of top interpretability proved to be effective in terms of accuracy and interpretability. Furthermore, if we were to judge features extracted by such a network as unconvincing, then our approach is a highly efficient method of falsification. Lastly, the success of this study-performed on a small-scale identificational problem-suggests that a similar approach could yield better results on a large-scale identificational or verificational problem.

Elucidating the relationships between two automated handwriting feature quantification systems for multiple pairwise comparisons

Recent advances in complex automated handwriting identification systems have led to a lack of understandability of these systems' computational processes and features by the forensic handwriting examiners that they are designed to support. To mitigate this issue, this research studied the relationship between two systems: FLASH ID^® , an automated handwriting/black box system that uses measurements extracted from a static image of handwriting, and MovAlyzeR^® , a system that captures kinematic features from pen strokes. For this study, 33 writers each wrote 60 phrases from the London Letter using cursive writing and handprinting, which led to thousands of sample pairs for analysis. The dissimilarities between pairs of samples were calculated using two score functions (one for each system). The observed results indicate that dissimilarity scores based on kinematic spatial-geometric pen stroke features (e.g., amplitude and slant) have a statistically significant relationship with dissimilarity scores obtained using static, graph-based features used by the FLASH ID^® system. Similar relationships were observed for temporal features (e.g., duration and velocity) but not pen pressure, and for both handprinting and cursive samples. These results strongly imply that both the current implementation of FLASH ID^® and MovAlyzeR^® rely on similar features sets when measuring differences in pairs of handwritten samples. These results suggest that studies of biometric discrimination using MovAlyzeR^® , specifically those based on the spatial-geometric feature set, support the validity of biometric matching algorithms based on FLASH ID^® output.

The factors influencing the identification of the chronological intersecting sequence between ink and toner

Identifying the formation time of a document is a problem forensic document examiners often face. It is understood that intersections with different intersecting sequences made by the same laser printer and the same gel pen are distinct from each other under coaxial light, and the appearance of an oil film or bright metallic marks in the regions of interest can be used as the basis to identify that the ink is above the toner. However, the characteristics of intersections may be influenced by a number of factors. Studying the characteristics of the intersections formed by laser-printed graphics and handwriting strokes made with a gel pen in different intersecting sequences can help us determine the formation sequence of each part on a questioned document. In this manuscript, samples were made using three pen types and two laser printers. A Leica stereo microscope M205A was used to capture the apparent morphology of the intersections. Microspectrophotometry spectra of all intersections were collected in reflectance mode using a video spectral comparator 6000 (VSC6000), and the resultant data were measured and analyzed in Statistical Product and Service Solutions 26.0 (SPSS). The results showed that 92.5% absolute accuracy was achieved from blind tests, and the intersecting sequence can be determined using the optical data of the intersections with an accuracy of up to 97.5% through discriminant analysis under ideal conditions.

The assessment of the impact of induction spatial effects on magnetic flux measurements of toner-printed documents to the detection of forged or altered documents

Magnetic flux measurements of toners can aid in the rapid differentiation of toner-printed specimens in the context of investigations of forgeries or alterations of printed documents. However, some variables that may impact magnetic flux measurements, including hysteresis effects, are not currently well understood. This study assessed the impact of hysteresis and other induction spatial effects on magnetic flux measurements of toners analyzing five toner-printed samples produced from different devices. The samples were printed with controlled grids of square, rectangular, and elongated rectangular blocks with the same area. Thirty measurements were conducted on each sample, on each grid type. The measurements were repeated in planes of rotation 90°, 180°, and 270° counter to this original position. The values obtained for the square grids were evaluated using one-way ANOVA to assess the presence and impact of hysteresis effects. The values obtained for the rectangular grids were compared with those obtained for the square grids using a two-way ANOVA to determine potential induction current orientation effects. The results of both one-way and two-way ANOVA were significant with p < 0.05, indicating that both hysteresis effects and induction current spatial effects contribute significantly to variations in magnetic flux measurements. Results confirmed that sensor orientation is an important factor that must be accounted for in method protocols for the measurement of magnetic flux of toners. Controlling these variables is a step forward toward the development of a reliable screening method to be deployed in the context of investigations of document forgeries or alterations.

Measuring the frequency occurrence of handwritten numeral characteristics-An expanded list

In the third of a series of studies and reports, the authors expand on the frequency occurrence proportions of various handwritten features. The first study culminated in the publication of "Measuring the Frequency Occurrence of Handwriting and Handprinting Characteristics." That study was followed by "Measuring the Frequency Occurrence of Handwritten Numeral Characteristics." The premise of this current and future follow-up studies is to expand on the initial lists of information incrementally by expanding the number of features and the number of writers. This study expands on the list of numeral features. A total of 34 numeral features was selected by the authors as candidates for this study and tested through an attribute agreement analysis. Based on the results of the testing, 17 new features have been added to the list of proportions. The original 1410 handwritten numeral specimen forms were utilized and pared to 1024 to obtain a proper population sampling for the United States. Interdependency testing was conducted on 783 pairs of inter-character numerals. A coefficient of correlation between -0.2 and +0.2 was found in 534 (68.20%) of these pairs. As of this report, there are now a total of 42 numerals with measured frequencies of occurrence. This material has already borne fruit as the combined frequency of occurrence studies were explained during an unsuccessful exclusion hearing in court with an explanation as to how these studies support the reliability of forensic document examination.

Experimental Research on Class Identification with a New Type of Erasable Gel Pens

A new type of erasable gel pen ink is becoming increasingly popular because of the modifiable characteristics for writing on documents. This study attempts to distinguish 12 types of blue and black erasable gel pens produced by mainstream stationery manufacturers using infrared (IR) visual analysis, Fourier transform infrared (FTIR) analysis, fluorescence analysis, and microspectrophotometry. The results demonstrate that IR visual, FTIR, and fluorescence analysis can be used to help distinguish each type of erasable gel ink. While microspectrophotometry can be used to effectively differentiate the blue gel inks in this study, there are limitations with respect to distinguishing black erasable gel pens. When these four optical analyses methods were used in combination, the gel inks could be accurately distinguished.

Distinguishing Characteristics of Robotic Writing

Advances in robotic handwriting technology create new challenges for forensic document examiners. In the past, devices such as the autopen were used to replicate signatures of government officials and corporate companies. In today's technology, companies such as Bond utilize robots to create written documents, which mimic natural patterns of handwriting. They generate customizable written samples by simulating pen movements and letter formations. Four forensic document examiners were given various reproduced questioned documents and utilized a modified ACE-V (analysis, comparison, evaluation, verification) methodology to determine their genuineness. Examiners were able to make a distinction between the human writing samples and the skilled robotic equivalents. Several distinct features that are not seen in natural handwriting, such as even pen pressure and the superimposition of letterforms were observed in the robotic samples. Careful examination of identifying features of the Bond produced documents resulted in an opinion of nongenuineness.

Exploitation of the Ultraviolet Properties and Machine Cut Edges of Paper to Associate and Sequence Sheets in a Ream

Previously unreported line patterns visible under ultraviolet light were observed on a proportion of plain white A4 printer/copier paper from different manufacturers. These Ultraviolet Line Patterns (UVLPs) usually appear as stripes down the vertical length of the paper. Typically, the UVLPs were found to "repeat" through the ream in a predictable way, while also changing. It is postulated that the repeating nature of the UVLPs is a result of the way that paper is manufactured. This leads to the ability to sequence the sheets compared to their original source paper. Even in the absence of UVLPs, it is possible to use our observation of the manufacturing process to anticipate the order of several sheets of paper and conclusively associate them, in some cases, by physically fitting their machine cut edges and crossing paper fibers. Such a novel approach to examining questioned documents would be highly useful in forensic casework.

Forensic Application of X-ray Fluorescence Spectroscopy for the Discrimination of Authentic and Counterfeit Revenue Stamps

Energy-dispersive X-ray fluorescence (ED-XRF) spectroscopy with data treatment via chemometric tools was explored as an analytical protocol to discriminate between authentic and counterfeit revenue stamps. Untreated samples were directly analyzed, and the discrimination was based on the characterization of constituent elements present in the inks and paper. Authentic samples and samples that were suspected of being counterfeit were analyzed at three different areas on their surfaces: the ink-printed area, the non-printed area, and the holographic area. Principal component analysis (PCA) was applied to the data to discriminate between authentic and counterfeit revenue stamps. Major differences in the elemental composition were noted (according to chemometrics and t-test, p < 0.05), and ED-XRF spectroscopy plus PCA protocol is proposed for use by non-specialist operators to screen for counterfeit stamps.

The Influence of Lying Body Position on Handwriting

Although the problem of handwriting variability due to lying body position has practical significance, particularly for last will cases, it has not been sufficiently studied. The presented experiment aimed to recognize how such posture may influence handwriting features. Samples of text and signatures were collected from 50 healthy individuals, aged 23-58, produced in three postures: typical sitting position (SP) and two different lying positions (LP1 & LP2). Using the SP sample of each individual as a specimen, eleven characteristics in LP1 and LP2 samples were evaluated as similar or different. Nine other features were measured with a specialized software, and their conformity was tested with Student's t-test. Although none of the characteristics differed significantly in most cases, variation occurred in pen pressure, margins, baselines, and heights of letters. Additionally, a series of blind tests revealed that lying position of the individuals did not hinder the possibility to identify their writings.

Dynamic characteristics of signatures: effects of writer style on genuine and simulated signatures

The aims of this study were to determine if computer-measured dynamic features (duration, size, velocity, jerk, and pen pressure) differ between genuine and simulated signatures. Sixty subjects (3 equal groups of 3 signature styles) each provided 10 naturally written (genuine) signatures. Each of these subjects then provided 15 simulations of each of three model signatures. The genuine (N = 600) and simulated (N = 2700) signatures were collected using a digitizing tablet. MovAlyzeR(®) software was used to estimate kinematic parameters for each pen stroke. Stroke duration, velocity, and pen pressure were found to discriminate between genuine and simulated signatures regardless of the simulator's own style of signature or the style of signature being simulated. However, there was a significant interaction between style and condition for size and jerk (a measure of smoothness). The results of this study, based on quantitative analysis and dynamic handwriting features, indicate that the style of the simulator's own signature and the style of signature being simulated can impact the characteristics of handwriting movements for simulations. Writer style characteristics might therefore need to be taken into consideration as potentially significant when evaluating signature features with a view to forming opinions regarding authenticity.

Application of micro-attenuated total reflectance Fourier transform infrared spectroscopy to ink examination in signatures written with ballpoint pen on questioned documents

Questioned documents examined in a forensic laboratory sometimes contain signatures written with ballpoint pen inks; these signatures were examined to assess the feasibility of micro-attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectroscopy as a forensic tool. Micro-ATR FTIR spectra for signatures written with 63 ballpoint pens available commercially in Korea were obtained and used to construct an FTIR spectral database. A library-searching program was utilized to identify the manufacturer, blend, and model of each black ballpoint pen ink based upon their FTIR peak intensities, positions, and patterns in the spectral database. This FTIR technique was also successfully used in determining the sequence of homogeneous line intersections from the crossing lines of two ballpoint pen signatures. We have demonstrated with a set of sample documents that micro-ATR FTIR is a viable nondestructive analytical method that can be used to identify the origin of the ballpoint pen ink used to mark signatures.

Kinematics of signature writing in healthy aging

Forensic document examiners (FDE) called upon to distinguish a genuine from a forged signature of an elderly person are often required to consider the question of age-related deterioration and whether the available exemplars reliably capture the natural effects of aging of the original writer. An understanding of the statistical relationship between advanced age and handwriting movements can reduce the uncertainty that may exist in an examiner's approach to questioned signatures formed by elderly writers. The primary purpose of this study was to systematically examine age-related changes in signature kinematics in healthy writers. Forty-two healthy subjects between the ages of 60-91 years participated in this study. Signatures were recorded using a digitizing tablet, and commercial software was used to examine the temporal and spatial stroke kinematics and pen pressure. Results indicated that vertical stroke duration and dysfluency increased with age, whereas vertical stroke amplitude and velocity decreased with age. Pen pressure decreased with age. We found that a linear model characterized the best-fit relationship between advanced age and handwriting movement parameters for signature formation. Male writers exhibited stronger age effects than female writers, especially for pen pressure and stroke dysfluency. The present study contributes to an understanding of how advanced age alters signature formation in otherwise healthy adults.

Handwriting Evidence in Federal Courts - From Frye to Kumho

In federal courts, the admissibility of scientific expert testimony in the last century has been governed by three major standards. The first of these standards, the "general acceptance" test, arose from the 1923 Frye v. United States (Frye) and required that any technique or method introduced in court be generally accepted by the relevant community of scientists. The more liberal "relevancy" standard of the Federal Rules of Evidence was enacted in 1975, and required the expert witness to be qualified by knowledge, skill, experience, training, or education. Finally, the "reliability" standard stated in the Daubert v. Merrell Dow Pharmaceuticals, Inc. (Daubert) opinion was handed down by the U.S. Supreme Court in 1993, supplanting the Frye general acceptance test as the sole determining factor in considering the admissibility of scientific expert testimony, and suggesting falsifiability, peer review and publication, and error rate as additional factors useful in evaluating a scientific technique. Changing views on expert testimony have also resulted in published criticisms of several forensic fields, especially those with subjective components. The first such field to be questioned, which also has been the subject of great debate, is expert handwriting identification. Challenges leveled against handwriting identification began with a law review article published in 1989 (and two subsequent articles); other challenges have been based on the requirements outlined in the Federal Rules of Evidence and Daubert. These challenges resulted in several court opinions with disparate views of handwriting identification, though testimony by an expert in the field was not rejected. In U.S. v. Starzecpyzel, handwriting evidence was admitted as nonscientific expert testimony under the Federal Rules of Evidence after failing a review under the factors outlined in Daubert. In U.S. v. Velasquez (Velasquez), the testimony of a document examiner was accepted, while the testimony of an expert critic of handwriting identification was rejected by the district court; however, on appeal, the Third Circuit held that both witnesses met the requirements of the Federal Rules of Evidence, and thus both testimonies were admissible. U.S. v. Jones (Jones) demonstrated yet another situation, where handwriting identification was challenged under Daubert. There the court found that because handwriting identification was never viewed as scientific evidence under Frye, it should not therefore be reviewed under Daubert. The Jones court admitted handwriting identification as nonscientific evidence, but stated that admissibility of nonscientific evidence should be governed by the facts of future cases. After some time and many other opinions on the admissibility of expert testimony under Daubert, several federal circuits permitted review of nonscientific expert testimony under the factors outlined in Daubert, while other federal circuits restricted such reviews only to purportedly scientific testimonies. In the latter arenas, determining whether handwriting identification was a scientific field or not had bearing on how it was reviewed for admissibility, if it was reviewed at all. This situation ended in March 1999 with the U.S. Supreme Court opinion of Kumho Tire Co., Ltd. v. Carmichael (Kumho), which held that the Daubert factors may be used for review of all expert testimony as the courts see fit, regardless of whether the field is considered scientific. In the wake of Kumho, two other cases challenged handwriting identification: U.S. v. Paul (Paul) and U.S. v. Hines (Hines). The Paul case, like Velasquez, dealt with exclusion of an expert critic of handwriting identification, and also like Velasquez, the court appeared to rely on the Federal Rules of Evidence rather than the factors outlined in Daubert to form its judgment. Hines, however, represented a significant departure from earlier cases, as handwriting identification was partially excluded in that the document examiner was permitted to testify to similarities and differences but was not allowed to opine as to the authorship. In sum, the federal courts are currently evaluating the admissibility of handwriting identification in a variety of ways. Though handwriting identification continues to be widely admitted as a form of expert testimony, the recent changes in admissibility requirements and challenges from the legal community have generated a climate where admissibility should no longer to be taken for granted. Because Kumho is a relatively recent case, its long-term effects on the admissibility of many fields of forensic science, including handwriting identification, are yet unknown.

Application of Fluorescence Spectroscopy to Forensic Science

Over the last decade, both ultraviolet and infrared fluorescence techniques have been applied to a number of areas of forensic science. Much of this work has been spurred on by the development of laser methods of visualization. One of the major beneficiaries of this attention to lasers and fluorescence has been in fingerprints. A great deal of research has been done on the development of new fluorescent dyes for visualizing fingerprints with a laser. Fluorescence has also been applied extensively to questioned-document analysis, principally in characterization of inks. Other types of evidence that use fluorimetric analysis include drugs, glass, petroleum products, and biological samples. This article will discuss these applications to forensic science and their advantages relative to other methods of analysis.

Chromatographic Analysis of Inks for Forensic Science Applications

This article reviews the use of chromatography for the separation and comparison of ink components. Thin layer chromatography (TLC) is the standard chromatographic procedure presently employed for the comparison of inks. Thin layer chromatography systems are described for the separation of different types of ink. The greater sensitivity and resolution offered by high performance liquid chromatography (HPLC) make it an attractive alternative to TLC for ink analysis, and recent work in this field is also outlined. Both techniques have been used for the measurement of changes occurring in the composition of inks with time, as a means of determining the age of an ink. Related analytical techniques, recent research, and future trends in ink analysis are also described.

Document Examination: Applications of Image Processing Systems

Dealing with images is a familiar business for an expert in questioned documents: microscopic, photographic, infrared, and other optical techniques generate images containing the information he or she is looking for. A recent method for extracting most of this information is digital image processing, ranging from the simple contrast and contour enhancement to the advanced restoration of blurred texts. When combined with a sophisticated physical imaging system, an image pricessing system has proven to be a powerful and fast tool for routine non-destructive scanning of suspect documents. This article reviews frequent applications, comprising techniques to increase legibility, two-dimensional spectroscopy (ink discrimination, alterations, erased entries, etc.), comparison techniques (stamps, typescript letters, photo substitution), and densitometry. Computerized comparison of handwriting is not included.