Application of Video Spectral Comparator (absorption spectra) for establishing the chronological order of intersecting printed strokes and writing pen strokes

The sequence of intersecting strokes of laser printers (black, blue, red and green) and typewriter ink (black) with the strokes of gel pen ink, ballpoint pen ink and fountain pen ink (black, blue, red and green) has been determined by studying their absorption spectra. The absorption spectra have been generated for each of the two pure inks (i.e. A and B) and points of their intersections (i.e. A over B and B over A) by using Video Spectral Comparator (VSC-2000-HR). The study was carried out with an assumption that the peak characteristics of spectra from the point of intersection should correspond to the peak characteristics of pure ink which was executed later. It was observed that the absorption spectrum of intersection corresponds with either the laser printer or the typewriter ink stroke, whether these strokes were executed earlier or later than the writing instrument strokes. As the results obtained from the study were negative, the FDEs are advised against the practice of this technique in the examination of the sequence of intersecting strokes for these specified inks.     

文件制作时间检验的物质基础

随着科学技术的快速发展,各种新型染料、颜料不断涌现。不断发展的书写和打印材料对文件制作时间检验工作提出了越来越高的要求。寻求显色物质整体稳定中的可测定因素,探索可资利用的指标性参数,达到检验目的。这就需要我们对材料进行比较全面的认识和研究。     

Identification of colorants in pigmented pen inks by laser desorption mass spectrometry

Pigments are rapidly replacing dyes as colorants in pen and printer inks, due to their superior colors and stability. Unfortunately, tools commonly used in questioned document examination for analyzing pen inks, such as TLC, cannot be used for the analysis of insoluble pigments on paper. Laser desorption mass spectrometry is demonstrated here as a tool for analyzing pigment-based pen inks. A pulsed nitrogen laser can be focused onto a pen stroke from a pigmented ink pen on paper, and positive and negative ions representative of the pigment can be generated for subsequent mass spectrometric analysis. Targeted pens for this work were a set of Uni-ball 207 pigmented ink pens containing blue, light blue, orange, green, violet, red, pink, and black inks. Copper phthalocyanine was identified as the pigment used to make both blue inks. A mixture of halogenated copper phthalocyanines were identified in the green ink. Unexpectedly, the pink ink was found to contain a red pigment, Pigment Red 12, treated with a mixture of water-soluble dyes. Each sample yielded ions representative of the pigments present.     

Determining Line-Crossing Sequences Between Laser Printing and Writing Pen Using Coaxial Light

Determining the application sequence of hand-written pen ink and printer toner lines has attracted significant interest in questioned document examination. This study uses coaxial light to determine line-crossing sequences, with intersections observed under a VSC600 forensic document workstation and a Leica M205A Stereo-microscope. Results show that reflected light at intersections and color contrast between intersections and nonintersections was observed when a hand-written ink line passes over a toner line, while a toner line passing over a written line appeared dull, with no color contrast. The procedure was tested under a range of conditions, such as types of writing pens and laser printers, the writer, and writing pressure, with the latter playing an important role in the evaluation. To validate the results, a 90% detection rate and 98% accuracy rate were achieved from 50 samples of blind testing, which is more effective than optical microscopy.     

无交叉笔画状态下激光打印文字与中性笔书写文字形成时序的实验研究

目的探索无交叉笔画状态下激光打印文字与中性笔书写文字的时序特征及变化规律,以求运用于案件检验。方法以两种不同时序,请5名志愿者分别执不同中性笔在120张A4纸张上书写文字,并使用4台不同型号激光打印机打印文字,再运用奥博视频层晰显微镜对实验样本进行放大观察。结果证实在两种时序条件下制作的实验样本之间存在诸多差异性特征。结论这些差异性特征为准确判定无交叉笔画状态下激光打印文字与中性笔书写文字的时序提供了基础实验依据。     

Preliminary Study on Determining the Sequence of Intersecting Lines by Fluorescence Technique

The determination of the sequence of intersecting lines is an important part of questioned document examinations. A fluorescence technique was used to determine the sequence of heterogeneous intersecting lines produced using inkpad ink, stamp‐pad ink, ballpoint pens, gel pens, fountain pens, colorants of carbon paper, photocopiers, laser printers, and inkjet printers. A SteREO Discovery.V20 equipped with the ZEN Blue Lite software was chosen to perform the tests.As the results obtained from the study were positive under most conditions, the fluorescence technique was found to be very successful in determining the sequence of intersecting lines from ballpoint pen, gel pen, fountain pen, photocopier, laser and inkjet printers, and inkpad inks. The method was also successful in determining the sequence of intersecting lines from ballpoint pen, photocopier, laser printer, and stamp‐pad inks under most conditions. The technique was not successful in determining the order of crossing lines blending together.     

利用暗记特征鉴别彩色激光打印、复印文件

目的探讨激光打印机的暗记特征,为鉴别彩色激光打印、复印文件找到一种有效的方法。方法根据不同物质对光的反射特性及蓝色与黄色互补特性的原理,采用420nm左右蓝光照射方法,对部分品牌彩色激光打印、复印文件进行了初步分析研究,总结了暗记点阵形态特征、小点形态特征、出现位置特征和排列含义等特征。结果此方法对彩色激光打印、复印机具的种类鉴别和个体鉴别简便、有效。     

Application of Raman spectroscopy in forensic investigation of questioned documents involving stamp inks

Stamp pad inks from different manufacturers across India have been analyzed to investigate the feasibility of Raman scattering as a tool for forensic analysis of questioned documents involving stamp inks. Nine different stamping inks were analyzed by both Raman spectroscopic and HPTLC methods. The results demonstrate the effectiveness of these methods in classifying the investigated stamping inks based on their spectral pattern and HPTLC chromatogram. Raman scattering tool was able to determine the sequence of heterogeneous intersection strokes involving a blue stamp pad ink and other writing instruments, such as ballpoint pen ink (red and black), pencil and laser printer toner. However, this method was unable to resolve the exact sequencing for the intersection strokes involving investigated stamp ink and blue ballpoint ink or gel pen ink (all colors).     

Evaluation of desorption/ionization mass spectrometric methods in the forensic applications of the analysis of inks on paper.

Fast atom bombardment and laser desorption mass spectrometry (LDMS) provide molecular level information concerning an ink's composition. Two ink-jet printer inks, Ink A containing the cationic dye Methyl Violet 2B, and Ink B containing the anionic dye, Solvent Black, were studied. Both positive and negative ion detection modes of the mass spectrometer were used. LD may be used for the analysis of inks on paper. Once on paper, the ink's solvent system has evaporated, leaving mainly the dyes behind, which are detected using LDMS. An ink fades with time, indicating that the dyes are degrading. Preliminary results from an accelerated aging study of ballpoint pen ink using UV irradiation confirm that dye degradation products are formed. The degradation chemistry follows an oxidative demethylation process for which all products formed are detected using LDMS. Results suggest that LDMS may be developed to determine the relative age of inks.     

Differentiation of coloured inks of inkjet printer cartridges by thin layer chromatography and high performance liquid chromatography

Document examiners are frequently asked to determine whether or not a colour printout has originated from a particular inkjet printer. The printer can rarely be identified unless some unique defects or irregularities of the printer are present on the printout. However, it is possible to decipher the make and/or model of the printer by comparing the ink-profile of the questioned printout with that of a seized inkjet printer cartridge or from one in a database. This paper presents an overview of a systematic approach to characterising and discriminating the inks of different inkjet printer cartridges using thin layer chromatography (TLC) and high pressure liquid chromatography (HPLC) with multi-wavelength ultra-violet/visible (UV/Vis) detection. Ink samples from 23 different inkjet printer cartridges (including originals and substitutes) of different brands and colour printouts, printed by known printers were examined with newly developed chromatographic methods. Subsequently, a database of the ink-profiles was generated. The methods provide a useful tool for discriminating coloured inks in inkjet printer cartridges of different brands.     

笔压特征在文件检验中的应用

文件检验学理论发展到今天，从某种意义上说已经比较成熟了。但是在实际检案中如何利用好各种有价值的特征，寻找案件的切入点和突破口。为鉴定结论提供充分的依据。则是我们每个文件检验工作者需要不断总结的。笔者发现。笔压（笔力）特征不仅是同一性鉴定中经常应用的一个特征。并且在判断文件的添加变造等方面也可发挥重要的作用。本文通过两起案件的介绍。分析了笔压特征的特点。并探讨了笔压特征的观察方法及其在文件检验中应用的要点。     

A Prototype of Mathematical Treatment of Pen Pressure Data for Signature Verification

A prototype using simple mathematical treatment of the pen pressure data recorded by a digital pen movement recording device was derived. In this study, a total of 48 sets of signature and initial specimens were collected. Pearson's correlation coefficient was used to compare the data of the pen pressure patterns. From the 820 pair comparisons of the 48 sets of genuine signatures, a high degree of matching was found in which 95.4% (782 pairs) and 80% (656 pairs) had rPA > 0.7 and rPA > 0.8, respectively. In the comparison of the 23 forged signatures with their corresponding control signatures, 20 of them (89.2% of pairs) had rPA values < 0.6, showing a lower degree of matching when compared with the results of the genuine signatures. The prototype could be used as a complementary technique to improve the objectivity of signature examination and also has a good potential to be developed as a tool for automated signature identification.     

A lifting process for determining the writing sequence of two intersecting ball-point pen strokes

The authors describe a technique for determining the order in which two intersecting ball-point pen strokes were made by means of lifting part of the ink with KromeKote paper. The KromeKote paper is applied to the intersection with the glossy side against the writing. The back of the lifting paper is rubbed with a blunt pointed instrument using moderate pressure. Study of the lift under low magnification discloses a pattern of edge markings with those from the last written line dominating the intersection. Results show a high percentage of accuracy.     

墨水书写时间测定的进展

本文追述了从20世纪20年代初到90年代末书写墨水的时间测定的进展.这包括,介绍新检验方法建立所需遵循的基本要求;推荐目前案件检验的工作程序,即墨水种类的确定,可疑文件的外观检验,同牌号、同配方、同批号比对样本的寻找;评述目前已为办案使用的各种书写年代测定的方法,如扩散法,转印法,染料比值法,气相色谱法、溶剂萃取法,差示扫描量热法等;以及讨论了有望用于年代测定的一些新技术,如用于钢笔墨水的电化学法,光谱法和用于圆珠笔墨水的显微分光光度法,付里叶变换拉曼光谱法等.     

A study to investigate the evidential value of blue gel pen inks

The aim of this project was to investigate the evidential value of blue gel pen inks in Europe. For this purpose, 33 blue gel pen inks, of different brands and models, representative of those available on the European market at the time of the study, were analyzed using three techniques: filtered light examination (FLE), Raman Spectroscopy (RS), and scanning electron microscopy (SEM). First, after visual examination (naked eye and stereo microscope), it was possible to classify the 33 inks into three groups described as: milky, metallic, and normal. This paper describes in detail the results obtained for the normal gel pen group. The ability of the techniques to discriminate gel inks between and within brands varied. The results indicated that RS and SEM were more discriminating than FLE. The greatest degree of differentiation was achieved when using a combination of RS and SEM techniques (discriminating power = 0.91). This study also highlights some problems concerning the identification of the brand of a gel pen from a written text.     

Recent developments in writing sequence determination

Two modifications of the Igoe-Reynolds lift technique for examination of line margins to determine the sequence of intersecting ball-point pen strokes are proposed. One for handwriting-typewriting intersections and the other extending the lift technique to ball-point pen writings of some age that are otherwise insensitive to the lift efforts.Attention is also directed to the increased usefulness of spectular light reflection examination resulting from changes in writing materials and instruments, particularly as applied to handwriting-typewriting sequence determination. An inexpensive, readily improvised vertical illuminator is described suitable for use with stereomicroscopes and cameras.     

The effects of latent print processing on questioned documents produced by office machine systems utilizing inkjet technology and toner

Counterfeiting of currency and identity documents, death threats, illegitimate business transactions, and terrorist-related activities are some examples of the types of crimes that often involve documents produced from printers and copiers. Although standard protocol typically requires a questioned document (QD) examination prior to latent print (LP) processing, occasionally, items of evidence may be submitted for a QD examination following the application of a series chemicals utilized in the development of latent fingerprints. In such cases, the forensic examiner must take into account any previous treatments prior to initiating an examination on documents produced with a printer or copier. This study was devised to examine the effects of a latent print development technique [ninhydrin, physical developer, and a bleach enhancer] on the physical and chemical examination of documents produced from copiers and printers.     

显微共焦激光拉曼光谱仪分析激光打印黑色墨粉字迹

激光打印机是常用办公设备,案件中经常会涉及到激光打印文件的检验,运用显微共焦激光拉曼光谱仪检验激光打印黑色墨粉字迹是一种快速、无损、灵敏度高的检验方法,可以对墨粉成分进行定性分析,在司法实践中,此种方法对激光打印黑色墨粉具有较好的检验效果,应用前景广阔。     

Does ink age inside of a pen cartridge?

In questioned document examination and ink dating, it has been assumed that the ink inside of a pen cartridge does not begin aging until the ink is dispensed onto paper. Positive ion laser desorption (LD) mass spectra were obtained of ink-on-paper samples containing methyl violet, from new and old pens. Mass spectral studies with methyl violet have established the mechanism for how the dye degrades over time, and have provided structural information concerning the dye's degradation products. This information was used as an indication of the relative age of ink on paper. The LD mass spectrum of the ink from a new pen was indicative of "new" ink, whereas the spectra of the ink found in some older pens may appear to be either new or old. The ink from most of the old pens studied appears not to have aged, supporting the common assumption, whereas other ink samples produced "aged" ink spectra, suggesting otherwise.     

Analysis of Pigmented Inkjet Printer Inks and Printed Documents by Laser Desorption/Mass Spectrometry*,†

Abstract: Anyone with a computer, scanner, and color printer has the capability for creating documents such as identification cards, passports, and counterfeit currency. Laser desorption mass spectrometry (LDMS) has been demonstrated as a powerful tool for colorant analysis. Inkjet printers are now moving largely toward the use of pigments as colorants; their insolubility makes analysis by simpler methods such as thin‐layer chromatography no longer an option. Recent developments in pigmented inkjet printer inks, such as gloss optimizers that coat pigment particles, may prohibit colorant analysis by LDMS. We demonstrate here that pigments used in inks from two Epson printers can be detected and analyzed by LDMS. Also, LDMS spectra of various colors created using a 4‐cartridge (cyan/magenta/yellow/black, CMYK) inkset are evaluated, to begin to develop an approach for unraveling LDMS data from real samples, to determine the number of inks used by a printer, and the chemical composition of the colorants.