Controlled electrostatic methodology for imaging indentations in documents

The electrostatic process for imaging indentations on documents using the ESDA device is investigated under controlled experimental settings. An in-house modified commercial xerographic developer housing is used to control the uniformity and volume of toner deposition, allowing for reproducible image development. Along with this novel development tool, an electrostatic voltmeter and fixed environmental conditions facilitate an optimization process. Sample documents are preconditioned in a humidity cabinet with microprocessor control, and the significant benefit of humidification above 70% RH on image quality is verified. Improving on the subjective methods of previous studies, image quality analysis is carried out in an objective and reproducible manner using the PIAS-II. For the seven commercial paper types tested, the optimum ESDA operating point is found to be at an electric potential near -400V at the Mylar surface; however, for most paper types, the optimum operating regime is found to be quite broad, spanning relatively small electric potentials between -200 and -550V. At -400V, the film right above an indented area generally carries a voltage which is 30-50V less negative than the non-indented background. In contrast with Seward's findings [G.H. Seward, Model for electrostatic imaging of forensic evidence via discharge through Mylar-paper path, J. Appl. Phys. 83 (3) (1998) 1450-1456; G.H. Seward, Practical implications of the charge transport model for electrostatic detection apparatus (ESDA), J. Forensic Sci. 44 (4) (1999) 832-836], a period of charge decay before image development is not required when operating in this optimal regime. A brief investigation of the role played by paper-to-paper friction during the indentation process is conducted using our optimized development method.     

Deciphering indented impressions on plastic

The questioned document laboratory is often called upon to decipher writing that has been erased, obliterated, or that has faded. In cases like these, the original writing is no longer legible to the naked eye, but may be enhanced using various light sources. Certain remnants of the ink's components absorb into the substrate's fibers and can be visualized, usually as luminescence or absorbance. A case is described here that involved the theft of a credit card. An empty plastic credit card holder was found in the possession of a suspect, and as submitted for examination. Indented impressions could be discerned on its clear plastic window and presumably originated from the credit card that had been held in the envelope. These indented impressions were deciphered in the hope that they would reveal enough details from the credit card to establish a connection between the plastic envelope and the stolen credit card. With methods generally utilized in the toolmarks and materials laboratory and the photography laboratory of the Israel Police, most of the indented impressions on the plastic were deciphered and a connection between the plastic envelope and the stolen credit card was demonstrated.     

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.     

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.     

Sequencing of intersecting lines by combined lifting process and scanning electron microscopy

The chronological order in which two intersecting writing or typed strokes were made can be determined for several combinations of writing media by scanning electron microscope (SEM) examination, a lifting and transfer technique using Kromekote paper, or a combination of the transfer technique followed by SEM examination of the remaining material in the intersection. When non-destructive examination cannot provide unambiguous determination of sequence, judicious choice by the document examiner of which technique to use for a given combination of writing media and paper type can be made using known characteristics of the materials involved. The range of line-crossings which can be reliably sequenced is greater using a combined transfer and SEM technique than when the examination is limited to either technique alone.     

Hyperspectral imaging of gel pen inks: An emerging tool in document analysis

Hyperspectral imaging (HSI) is a useful technique in the examination of writing inks, including gel pen inks, which combines digital imaging with % reflectance spectroscopy. This facilitates the detection of subtle differences between chemically similar inks. This study analysed a variety of blue, red and black gel inks on white office paper using HSI. The potential of the technique for ink discrimination compared to other analytical methods of examination is highlighted. Discriminating powers of 1.00, 0.90 and 0.40 were achieved using HSI for red, blue and black gel inks respectively. The overall discriminating power of 0.76 for the technique combined with its non-destructive nature and minimal sampling requirements demonstrates promise for this type of application.     

字本位和逻各斯中心主义两种证据观及其历史演变

本文重点讨论了两种证据观：字本位的证据观和逻各斯中心主义的证据观。并进一步认为，中国传统证据观是字本位性的。表现在言、文、象三重证据符号的关系中以“书写”或经典为中心。现代中国发生了证据观的革命性变化，主要表现为“去汉字化”的逻各斯中心主义证据观，即在言、文、象三重证据符号的关系中以“言、象”为中心。“去汉字化”建立了中国现代性证据现，同时也难以避免地导致了与传统文化的断裂。     

Potentiality of 3D laser profilometry to determine the sequence of homogenous crossing lines on questioned documents

The determination of the sequence of line crossings is still a current problem in the field of forensic documents examination. Optical examination, lifting technique, ESDA technique, and electron microscopy are the most widely used methods for the determination of the writing order of crossing texts. However, at present many examinations of intersecting lines result in an inconclusive opinion, particularly if the same type and colour of ink is involved. This paper presents the potentiality of the 3D laser profilometry, which has been to determine the chronological sequence of homogenous "crossing lines". The laser profilometry, illustrated in this paper, has been developed on a conoscopic holography based system. It is a non-contact three-dimensional measuring system that allows producing holograms, even with incoherent light, with fringe periods that can be measured precisely to determine the exact distance to the point measured. This technique is suitable to obtain a 3D micro-topography with high resolution also on surfaces with unevenness reflectivity (usual for the paper surface). The proposed technique is able to obtained 3D profile in non-invading way. Therefore, the original draft are not physically or chemically modified, allowing a multi-analysis in different times. The experiments performed with line crossings database show that the proposed method is able of "positive identification" of writing sequence in the majority of the tests. In absence of a positive identification, the result has been "inconclusive" (no false determination did occur in this work).     

法医学论文摘要的写作特点

目的探讨法医学论文摘要特别是英文摘要的写作方法。方法对目前国内医学杂志和法医学杂志的论文摘要进行分析比较和举例说明。结果国内医学杂志采用结构式摘要的写作方法，而国外法医学杂志一般采用叙述式摘要的写作方法。结论英文摘要是国际间信息交流的桥梁，掌握英文摘要的写作方法对于法医学者来说是十分重要的。     

Background correction in forensic photography. II. Photography of blood under conditions of non-uniform illumination or variable substrate color--practical aspects and limitations

The combination of photographs taken at wavelengths at and bracketing the peak of a narrow absorbance band can lead to enhanced visualization of the substance causing the narrow absorbance band. This concept can be used to detect putative bloodstains by division of a linear photographic image taken at or near 415 nm with an image obtained by averaging linear photographs taken at or near 395 and 435 nm. Nonlinear images can also be background corrected by substituting subtraction for the division. This paper details experimental applications and limitations of this technique, including wavelength selection of the illuminant and at the camera. Characterization of a digital camera to be used in such a study is also detailed. Detection limits for blood using the three wavelength correction method under optimum conditions have been determined to be as low as 1 in 900 dilution, although on strongly patterned substrates blood diluted more than twenty-fold is difficult to detect. Use of only the 435 nm photograph to estimate the background in the 415 nm image lead to a twofold improvement in detection limit on unpatterned substrates compared with the three wavelength method with the particular camera and lighting system used, but it gave poorer background correction on patterned substrates.     

Investigation of death through body writing: a case study

Various surfaces or substrates are often encountered in the examination of questioned writing; however, no writing is more interesting than that found on the human body nor more challenging when the writing in question is linked to a death investigation. The body of an 18-year-old male was brought to the State Crime Laboratory, Little Rock, Arkansas, with a gunshot wound to the head and several messages written on his arms and chest. This paper will discuss the examination of evidence used to determine the manner of death through a cooperative effort between the Medical Examiner's Section and the Questioned Document Section of the Crime Laboratory.     

圆珠笔油墨字迹书写时间鉴别的研究

圆珠笔油墨字迹书写时间的鉴别是摆在文件鉴定人员面前的棘手问题.本文作者借鉴国外的检验方法,经过近十年的探索,考查了各种因素的影响,研究出了适合我国国情的通过圆珠笔字迹油墨被溶解能力测试来确定其书写时间的鉴定技术,并且进一步发展了国外的检验方法,研制出了专用的检验器材,发明了模拟低温操作程序,使这一技术的适用范围更广.在有合适比对样本的情况下,可以准确鉴别落款时间在一年以上、怀疑书写时间在半年以内的可疑文件的真伪.     

Quantitative evaluation of europium in blue ballpoint pen inks/offset printing inks tagged with europium thenoyltrifluoroacetonate by spectrofluorometry and ICP-AES

Tagging of writing/printing inks with suitable inorganic taggants such as rare-earth chelates has the potential to help document examiners identify fraud in sensitive written/printed documents. Selection of rare-earth chelates as taggants primarily depends on the satisfactory sensitivity of analytical determination and the absence of the taggants in normal varieties of inks used for document writing/printing. Spectrofluorometric determination of trace amounts of europium in blue ballpoint pen inks and offset printing inks tagged with europium thenoyltrifluoroacetonate was carried out with sodium tungstate solution. Sodium tungstate acts as a specific reagent that enhances the fluorescence intensity of the Eu3+ ion. The excitation and emission wavelengths are 270 nm and 605 nm respectively. The results were compared with the data obtained with ICP-AES. Satisfactory recoveries were observed with precision better than 5% RSD and comparable accuracy. Under the optimized experimental conditions, detection limits and quantitation limits were determined. The detection limits obtained by spectrofluorometry and ICP-AES were 0.01 microg/mL and 0.006 microg/mL respectively whereas the limits of quantitation were about 0.03 microg/mL and 0.018 microg/mL respectively. The spectrofluorometric method is rapid, selective, sensitive and accurate for the determination of europium in blue ballpoint pen ink and offset printing inks and may be suitable for application in the examination of sensitive documents to aid in document related crime investigation. The advantages and limitations of the tagging approach and proposed analytical techniques are discussed.     

Application of laser induced breakdown spectroscopy to examination of writing inks for forensic purposes

The research was focused on the analysis of writing inks using the laser induced breakdown spectroscopy (LIBS) technique. 34 samples of blue, 30 of black, and 21 of red writing inks were analyzed under optimized conditions to determine the variation of chemical composition of inks between different colours, brands and types. Nine elements (Ba, Cr, Cu, Fe, Li, Mo, Mn, Ni and W) were taken into account during comparative analysis of inks. Because of the strong effect of the paper spectrum, elements often found in inks (Ca, Al, Mg, Na, Ti, and Si) were eliminated from LIBS analysis of inks. It was determined that the LIBS method is capable of revealing qualitative elemental differences between ink samples. The discrimination power of this method was found to be 83, 82 and 61% for blue, black and red inks, respectively. Inks produced by the same producer were able to be differentiated in some cases. The results showed the potential of LIBS for forensic purposes as an effective and robust technique, requiring a small amount of sample and giving analytical information in a very short time.     

Visualizing Indented Writing on Thermal Paper by the Controlled Application of Heat

Indented writing on thermal paper made with either one, two, or three sheets of paper above the thermal paper has been visualized by the controlled application of heat to the thermal paper at temperatures below the paper's normal color change temperature. Indentations created by applying a variable pressure to a steel letter stamp showed that, with one sheet above the thermal paper, indentations were more visible at lower pressures than with either two or three sheets above. Handwriting from 20 volunteers produced indented writing graded with most of the text clear and easy to read for all samples with one sheet above, half the samples with two sheets above and eight samples with three sheets above. Comparison with ESDA showed that, with three sheets above, there was a statistically significant difference (p < 0.01), with heating producing more samples than ESDA with most of the text clear and easy to read.     

论汉字笔迹字群结构习惯及特征

目的字群结构是汉字书写动作系统中高频率书写词汇而形成的特殊单字整体结构。其书写动作的习惯特性不同于单字书写动作系统,具有超出单字书写动作习惯的特性和特殊表现形式。因此对字群结构及其特征的研究有利于完善笔迹鉴定的特征体系,尤其是对签名字迹和具有职业习惯者书写的少量字迹的同一认定有一定价值。     

Preparing ballistic gelatine--review and proposal for a standard method

Meaningful assessment and comparisons on the injury potentials of various types of ammunition and credible forensic reconstruction require an agreement on standard tissue simulant. Gelatine blocks are relatively inexpensive and easy to produce and they meet most of the criteria for a good terminal ballistic simulant. This research looks into the variables of preparing ballistic gelatine and their effects on penetration resistance. It was found out that consistent quality gelatine blocks are easy to make and that the variables like water temperature have a far smaller effect than previously thought. Also water acidity variances allowed by European Council directive on drinking water do not have any measurable effect. A proposed standard method for gelatine preparation is presented together with penetration function for verification of gelatine quality.     

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.     

书写习惯未定型成年人笔迹检验

目的研究书写习惯未定型成年人笔迹的检验方法。方法通过实例研究分析成年人笔迹变化的特点和原因,确定笔迹性质和检验方法。结果书写习惯未定型也是成年人笔迹变化的重要原因。书写习惯未定型成年人笔迹是成年人正常笔迹的例外,适用正常笔迹检验方法。结论本研究确立了检材笔迹与样本笔迹非本质差异的判断标准,适用于短时间内变化较大的成年人笔迹的同一认定。     

签名笔迹及其检验研究

签名笔迹检验一直是文件检验中的难点,案件涉及比例居高,并呈上升之势。此类字迹,字符特征少,书写习惯反应不充分,检验难度大。因此,通过对签名笔迹主要类型、特点、检验方法等相关问题的探究,来增强对签名笔迹的认识以及提高签名笔迹检验的实践能力,意义重大。