The detection of multiply charged dyes using matrix-assisted laser desorption/ionization mass spectrometry for the forensic examination of pen ink dyes directly from paper

Abstract:  Laser desorption mass spectrometry (LDMS) is emerging as a technique for questioned document examination. Its use is limited to detecting ink dyes that are neutral or singly charged. Several inks contain dyes that are multiply charged and LDMS cannot be employed for their identification. We have successfully detected >20 polyionic dyes that can be used in the manufacture of inks using matrix-assisted laser desorption/ionization (MALDI) MS, directly from paper, with the matrix, 2-(4-hydroxyphenylazo)benzoic acid (HABA), and the additive, diammonium hydrogen citrate (DAHC). For example, Acid Violet 49, a charged dye containing one positively-charged site and two negatively charged sulfonate groups, cannot be detected by LDMS, but forms intact, singly charged ions in the MALDI MS experiment. The method described is also useful for identifying multiply charged dye mixtures that are used in modern pen inks.     

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.     

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.     

Study on the Method Used to Display Self‐fading Lines and Erasable Lines

Two new kinds of writing tools are popular in China's market. One is a self‐fading pen, and another is an erasable pen. The ink of the two kinds of writing tools has a remarkable characteristic that it can gradually fade or disappear under heat or be rubbed off. How to reveal the disappeared written lines is a very important question for document examiners. In this article, three series of ink line samples were made with five types of self‐fading pens, 18 types of erasable pens, and three types of papers. Temperature, humidity, and lighting are known as influential factors of the process, and the effect of fading was examined. Luminescence, ultraviolet (UV), sidelight, electrostatic indentation development,low temperature, and solution revealing methods are found to be effective methods used to reveal the disappeared written lines. The best operating conditions for each method were obtained from the conducted experiments.     

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.     

系统检验方法在可疑文件鉴定中运用

通过对近年来成功解决的几起可疑文件鉴定的典型案例分析,较详细地阐述在文件鉴定实践中,如何运用系统检验的思想,通过可疑文件上留下的细微变造痕迹,巧妙识别可疑文件的伪造手段和方法,为法庭提供科学、可信的证据,取信于法官、律师及当事人,使得案件最终圆满审结.在面对某些疑难案件的鉴定中,在鉴定思路和方法上对文件检验人员,有一定的启示作用.     

判决公开制度的现状及对策

判决公开是我国一项重要诉讼制度和宪法原则,但这一原则在实践中未能充分实现其制度价值。因此,相关部门要尽快改善基层法院的硬件设施,设立国家判例数据库,完备案例的检索功能;判决书选择公开出版或网络公开。     

“切开法”快速鉴定朱墨时序

朱墨时序是指印文与字迹形成的先后顺序。"朱"代表印文,"墨"指与印文形成交叠的字迹笔画。用"切开法"进行光敏印油、印泥印文和喷墨打印字迹、激光打印字迹、复印字迹的朱墨时序鉴定实验,取得了令人满意的效果。实验证明,"切开法",所需器材简单,操作简便,准确率高,对鉴定人从业经验也没有很高要求,非常适合基层一线单位使用。     

Determination of Trace Elemental Concentrations in Document Papers for Forensic Comparison Using Inductively Coupled Plasma–Mass Spectrometry

Abstract:  With improvements in manufacturing procedures, comparing physical characteristics of paper samples may not offer sufficient discrimination among different vendors. In this work, the potential to differentiate paper samples based on trace element concentrations was investigated. Paper samples from two different vendors were microwave-digested and trace element concentrations (Mg, Al, Mn, Fe, Sr, Y, Ba, Ce, and Nd) were determined using inductively coupled plasma–mass spectrometry. Differences in concentration were assessed statistically using two-way ANOVA and Tukey's honestly significant differences test. Elemental concentrations were shown to be consistent across a single sheet as well as within a single ream of paper for each vendor. Reams from vendor A were differentiated based on Al and Ba concentration while reams from vendor B were differentiated based on Mg, Mn, and Sr concentrations. Paper was differentiated according to vendor based on significant differences in Ba, Sr, Ce, and Nd concentrations.     

红外线合成图像在变造文件检验中的应用与分析

在文件检验中,黑白红外线照相是一种检验变造文件的方法,然而,在某些情况下效果欠佳。为了提高检验的准确性,不妨可以应用红外线合成图像的方法。应用Photoshop图像处理方法,根据红外线彩色照相的感光原理和色彩再现过程,对数码照相机拍摄的可见光图像和红外线图像进行适当处理,即可生成红外线合成图像。这种图像可以反映字迹对可见光和红外线的吸收与反射情况,通过判断字迹颜色有否改变来检验书写色料的异同。由此可见,利用红外线合成图像方法检验某些变造文件,可以获得黑白红外线照相无法得到的检验结果,这对提高鉴定结论的准确性具有实际应用价值。