The use of an electrostatic detection device to identify individual and class characteristics on documents produced by printers and copiers--a preliminary study

The market is inundated with inkjet printers, laser printers, and photocopiers, which are often used in criminal activities. Many of these office machines are built by various manufacturers, hence they are constructed with different hardware designs (e.g. "rolling" and "grabbing" mechanisms) that have changed over the years due to technological advances. Examinations of printed documents that involve the chemical analysis of ink colorants and the identification of physical machine defects such as trash marks are essential for the forensic examiner, but new techniques are needed to more closely identify a machine model or group of models. An electrostatic detection device (EDD) provide forensic examiners with a nondestructive method to examine indentations on a document. In this work, an EDD is used to detect latent physical markings left on documents by printers and photocopiers. Seventeen inkjet printers, 12 laser printers, and 3 photocopy machines were used to produce test documents. Physical markings were detectable in the large majority of the documents and were reproducible 100% of the time.     

Processes involved in the development of latent fingerprints using the cyanoacrylate fuming method

Chemical processes involved in the development of latent fingerprints using the cyanoacrylate fuming method have been studied. Two major types of latent prints have been investigated-clean and oily prints. Scanning electron microscopy (SEM) has been used as a tool for determining the morphology of the polymer developed separately on clean and oily prints after cyanoacrylate fuming. A correlation between the chemical composition of an aged latent fingerprint, prior to development, and the quality of a developed fingerprint has been observed in the morphology. The moisture in the print prior to fuming has been found to be more important than the moisture in the air during fuming for the development of a useful latent print. In addition, the amount of time required to develop a high quality latent print has been found to be within 2 min. The cyanoacrylate polymerization process is extremely rapid. When heat is used to accelerate the fuming process, typically a period of 2 min is required to develop the print. The optimum development time depends upon the concentration of cyanoacrylate vapors within the enclosure.     

Examination of the Sequence between Laser Printing and Rollerball Pen Writing Without an Intersecting Stroke

Examining the sequences of printing and writing is a significant method of determining the authenticity and validity of documents. Forensic document examiners have extensively studied crossing lines, which has produced useful information. However, the sequence for laser printing and rollerball pen writing without crossing strokes has not been studied. To solve this problem, volunteers were invited to write characters on A4 paper with different rollerball pens using two sequences. Four laser printers applied print to these sheets, and the materials were examined using an Optem A-Zoom2 video tomography microscope. Consequently, distinguishing features were noted between the materials produced in both sequences. These features might provide a scientific basis for accurately determining the sequence between laser printing and rollerball pen writing in the absence of intersecting strokes.     

Examination of spur marks found on inkjet-printed documents

In this paper, we propose the examination of spur mark evidence on inkjet-printed documents. Spur marks are tool marks created by the spur gears in the paper conveyance system of many inkjet printers. The relationship between printouts and printers were investigated by comparing the spur marks found on printed documents with reference spur marks sampled from known printers. The comparison was based on two characteristics of spur marks: pitch and mutual distance. These characteristics extracted the geometric features of spur marks and provided information on the type of spur gears and their location in the paper conveyance system. The spur marks on a printout matched the reference spur marks within three percent of the measured values. Spur marks were considered to be effective class characteristics to identify certain brands of inkjet printers since spur gears are used in many types of these machines.     

打印复印文件朱墨时序表观特征初探

本文详细介绍了一案例的检验过程,并通过简单实验对激光打印、静电复印形成文件的朱墨时序的表观特征进行了粗浅的探究。总体而言,两种时序在朱墨交叉点的表观特征上具有文字与印文均完整、肉眼感觉文字均压在印文之上的共同点;在两者本质的差异点上,先朱后墨表现为交叉点的墨粉与未交叉部位一致,先墨后朱表现为交叉点的墨粉光泽度增加、具有潮湿感、以及易出现水珠状的印油积聚现象。     

Classification algorithm using halftone features of counterfeit bills and CNN

With recent advancements in image processing and printing technology, home printers have improved in performance and grown more widespread. As such, they have been increasingly used in counterfeiting and forgery. Most counterfeit bills in Korea have been created using home scanners and printers. The identification of printer model is thus necessary to rapidly track down criminals and solve crimes. Household printers can be largely divided into inkjet and laser printers. These two types of printers print halftone textures instead of continuous images. This study proposed a technique of printer classification based on halftone textures that can be observed in printed documents. Since halftone textures are expressed as periodic lattices, the images were transformed via FFT, which is highly effective at expressing periodicity. ResNet, known for its superior gradient flow, was used for training. The experiment was conducted on 12 color laser jets and 2 inkjets. Scans of bills printed by each printer were used, and halftone texture analysis was performed on these images for printer model classification. Each image was cropped into several parts; one of the cropped parts was analyzed. The analysis showed that laser printers could be 100% distinguished from inkjet printers. An accuracy of 98.44% was achieved in make classification. When 50 cropped images were used instead of a single image, the technique achieved 100% accuracy in model classification. The proposed technique is non-destructive; it offers high accessibility and efficiency as it can be performed using a scanner alone, without requiring additional optical equipment.     

The Analysis of 3D Printer Dust for Forensic Applications,,

3D printers are becoming increasingly efficient and economical, and thus more widespread and easily accessible to consumers and businesses. They have been used to print nefarious objects such as guns and suppressors. Previous research has documented the release of dust particles during the printing process; however, little has been written about the morphology and chemical features that define the dust emitted by these printers. This study was undertaken to recover, analyze, and identify the dust produced during the printing process in the context of forensic trace evidence analysis. Samples were collected from a variety of 3D fused deposition modeler printers, representing both consumer and commercial grade models. This work focused on printers that use thermoplastic filaments composed of acrylonitrile butadiene styrene (ABS) or polylactic acid (PLA), two of the most commonly used filament polymers. Swabs were used to collect dust within the printer chamber and then processed to isolate the dust particles. Particles produced from ABS filaments are most easily recognized via light microscopy through a combination of color, morphology, and fluorescence. The composition of these particles can be confirmed through analysis by either FTIR or Raman microspectroscopy. These methods can also be used to identify ABS fillers and pigments within the printer dust particles. In contrast, dust from PLA printers consistently contained finer, submicron-sized particles that could be observed by field emission scanning electron microscopy. Because the size of the particles precludes their identification using vibrational spectroscopy methods, pyrolysis-GC-MS was used to confirm the presence of PLA.     

利用彩色文件上的图文特征鉴别喷墨打印机品牌

目的通过彩色文件上的图文特征鉴别喷墨打印机的品牌。方法在体视显微镜下观察采用不同喷墨机理的惠普、佳能和爱普生三大品牌喷墨打印机打印的彩色图文。结果通过对彩色图文上六种墨迹形态特征的比较,发现三大品牌喷墨打印机打印的彩色图文存在明显差异。结论依据这六种特征对三大品牌的喷墨打印机进行鉴别。     

常用彩色激光打印机打印文件暗记特征的初步研究

目的收集当前我国常用不同品牌和型号的彩色激光打印机打印样本,研究打印文件上暗记特征的提取分析及其变化规律,探讨彩色激光打印文件暗记特征在鉴定实践中的应用及其在打印文件防伪措施中的价值。方法使用显微镜、文检仪及有关图像处理技术分别检验了彩色激光打印机的打印文件样本。结果彩色激光打印机打印文件上会出现暗记特征,且不同品牌的暗记特征出现规律、形态特征和点阵特征不同。结论暗记特征可作为初步鉴别彩色激光打印机品牌型号及打印时间的依据,具有防伪价值,但其在鉴定实践中还存在一定的局限性,有待进一步研究。     

Classification of black powder toners on the basis of integrated analytical information provided by Fourier transform infrared spectrometry and X-ray fluorescence spectrometry

Differentiating between black powder toners used in laser printers and copiers can be challenging for forensic examiners. One hundred and sixty-two samples from 82 different types of cartridges produced by 21 manufacturers that are currently available on the Polish market were studied using Fourier transform infrared spectrometry (FT-IR) and energy-dispersive X-ray fluorescence spectrometry (XRF). The spectra obtained by these two methods were classified into 14 groups and 28 groups using FT-IR and XRF, respectively. These classifications served as a basis for the development of an analytical scheme for differentiating black powder toners. This scheme can be used with any two methods that supply different information about an examined sample. The research will show that if two samples are similar in polymer composition (e.g., FT-IR spectra), additional quantitative elemental composition from XRF analyses may provide more discrimination. It was possible to differentiate 82.5% pairs of examined samples using only FT-IR, 90.8% pairs of examined samples using only XRF, and 95.8% pairs of examined samples using these two methods. Obtained spectra and all the available information could be used to create/build a database. The results obtained confirm the multiplicity and compatibility of toners. Additionally, it was stated that not all the samples were original (OEM).     

An Examination of the Sequence of Intersecting Seal and Laser Printing Toner Line

Examining the sequence of intersecting seal and laser printing line is a significant method of determining the authenticity and validity of documents. In this study, five brands of stamp pad inks, three types of inkpads and seven kinds of laser printers were used to make heterogeneous line intersections. Observation method of physical characteristics, scraping technique and fluorescence method was used to determine the sequence of intersecting lines. Distinguishing features were noted between the materials produced in both sequences. As the results obtained from the study were positive, these features might provide a scientific basis for accurately determining the sequence between laser printing line and inkpad (stamp pad ink) seal.     

Application of capillary electrophoresis to examination of color inkjet printing inks for forensic purposes

In the process of questioned document examination, the discrimination of inkjet printing inks is becoming more necessary due to increasingly frequent counterfeiting of documents printed by inkjet printers. Therefore, a method based on micellar electrophoretic capillary chromatography (MECC) has been developed and applied to analysis of such inks extracted from paper. With the use of an optimized and validated analytical procedure, multielectropherograms of inks taken from various models of printers made by various producers (Hewlett-Packard, Epson, Brother, Lexmark and Canon) were created. It was shown that effective differentiation of individual inks was possible in terms of migration time, order and specific shapes of characteristic peaks. By comparison of recorded UV-Vis spectra, the identification of main dyes was also achievable. The usefulness of the method was confirmed by an intralaboratory test of utility, in which several forged printouts were successfully examined. The obtained results proved that the proposed procedure is a useful tool that could be applied to ink discrimination and group identification of dyes originating from inkjet printing inks. Consequently, the developed method can be applied in the forensic field, including investigation of the authenticity of documents.     

Cognitive issues in fingerprint analysis: inter- and intra-expert consistency and the effect of a 'target' comparison

Deciding whether two fingerprint marks originate from the same source requires examination and comparison of their features. Many cognitive factors play a major role in such information processing. In this paper we examined the consistency (both between- and within-experts) in the analysis of latent marks, and whether the presence of a 'target' comparison print affects this analysis. Our findings showed that the context of a comparison print affected analysis of the latent mark, possibly influencing allocation of attention, visual search, and threshold for determining a 'signal'. We also found that even without the context of the comparison print there was still a lack of consistency in analysing latent marks. Not only was this reflected by inconsistency between different experts, but the same experts at different times were inconsistent with their own analysis. However, the characterization of these inconsistencies depends on the standard and definition of what constitutes inconsistent. Furthermore, these effects were not uniform; the lack of consistency varied across fingerprints and experts. We propose solutions to mediate variability in the analysis of friction ridge skin.     

Enhancing the quality of aged latent fingerprints developed by superglue fuming: loss and replenishment of initiator

The recovery and identification of latent fingerprints from a crime scene are crucial to many investigations. The cyanoacrylate (superglue) fuming method (CFM), which develops fingerprints by growing a polymer coating over the print residue, is a powerful method but encounters severe limitations when prints are aged or exposed to harsh environmental conditions. We examine the aging process and how the changes that occur to a fingerprint residue over time influence the growth of polymer during development. We identify loss of initiator by erosion and degradation that, when coupled with a loss of water from the print residue, result in a decreased ability to polymerize ethylcyanoacrylate. Then, we present a methodology by which the ability of aged latent fingerprints to polymerize ethylcyanoacrylate is recovered. Two print enhancement agents, acetic acid and ammonia, are demonstrated to improve the growth of polymer from the print ridges by over an order of magnitude, while retaining the integrity of the print structure. Comparison between the two enhancement agents indicate that the enhancement occurs due to ridge coating by the ammonia or acetic acid and pH control of the latent print.     

Analyzing Brazilian vehicle documents for authenticity by easy ambient sonic-spray ionization mass spectrometry

Using desorption/ionization techniques such as easy ambient sonic-spray ionization mass spectrometry (EASI-MS), it is possible to analyze documents of Brazilian vehicles for authenticity, providing a chemical profile directly from the surface of each document. A method for the detection of counterfeit documents is described, and the falsification procedure is elucidated. Forty authentic and counterfeit documents were analyzed by both positive and negative ion modes, EASI(±)-MS. EASI(+)-MS results identified the presence of (bis(2-ethylhexyl)phthalate plasticizer and of dihexadecyldimethylammonium biocide in both types of documents. For EASI(-)-MS results, the 4-octyloxybenzoic acid additive ([M + H](+): m/z 249) is present only in counterfeit documents. It was also found that counterfeit vehicle documents are produced via Laserjet printers. Desorption/ionization techniques, such as EASI-MS, offer therefore, an intelligent way to characterize the counterfeiting method.     

针式打印文件检验的探讨

针式打印机是一种常用的办公机具,从针式打印机的结构和打印原理出发,阐述了针式打印文件种类鉴别和个体识别所依据的打印特征,为针式打印文件的检验鉴定进行操作层面的探讨。     

Visualizing latent fingerprints on color-printed papers using ultraviolet fluorescence

Laser detection of latent fingerprints on a white paper has been performed, previously. Ultraviolet fluorescence from various kinds of printer toner and ink used for home printers were measured to study fluorescence imaging of fingerprints on a color-printed white paper. The experimental system consisted of a nanosecond pulsed tunable laser and a cooled CCD camera. Excitation wavelengths are 230 and 280 nm. Fourteen printers consisting of three color laser printers, three color inkjet printers, five monochrome laser printers, two monochrome copy machines, and a color copy machine were tested. Toner and ink of most printers exhibited fluorescence in the region from 360 to 550 nm. In most cases, clear fluorescence images were obtained by time-resolved imaging with a band-pass filter and 280-nm excitation. However for toners from laser color printers that showed strong fluorescence, better results were obtained with 230-nm excitation. Latent fingerprints on a photograph page and a black-character page of a newspaper were also imaged.     

How do latent print examiners perceive proficiency testing? An analysis of examiner perceptions,performance, and print quality

Proficiency testing has the potential to serve several important purposes for crime laboratories and forensic science disciplines. Scholars and other stakeholders, however, have criticized standard proficiency testing procedures since their implementation in laboratories across the United States. Specifically, many experts label current proficiency tests as non-representative of actual casework, at least in part because they are not sufficiently challenging (e.g., [1], [2], [3], [4]. In the current study, we surveyed latent print examiners (n = 322) after they completed a Collaborative Testing Services proficiency test about their perceptions of test items. We also evaluated respondents’ test performance and used a quality metric algorithm (LQMetrics) to obtain objective indicators of print quality on the test. Results were generally consistent with experts’ concerns about proficiency testing. The low observed error rate, examiner perceptions of relative ease, and high objective print quality metrics together suggest that latent print proficiency testing is not especially challenging. Further, examiners indicated that the test items that most closely resembled real-world casework were also the most difficult and contained prints of the lowest quality. Study findings suggest that including prints of lower quality may increase both the difficulty and representativeness of proficiency testing in latent print examination.     

A Preliminary Study on Sources of Banding Artifacts for the Identification of Monochromatic Laser Printers,

The analysis of questioned documents printed with monochromatic toner has been a great challenge to document examiners. Banding artifacts, which are often perceived in the outputs of laser printers, could be a solution to the identification of printers. In this study, sources other than the gear transmission errors were discovered for some primary banding frequency components. By detecting the angular velocity variation of photosensitive drums and other rotating parts of the tested printers and comparing them with the banding signals extracted from the printouts, the authors located the sources of banding frequency components. It was shown that the sources of some primary and persistent banding signals, which were previously unknown, were traced to the periodic velocity variations of the motors or the timing belts. As inherent signatures, banding artifacts could be promising features for discriminating documents printed by individual laser printers.     

Reactions of latent prints exposed to blood

We explored whether an undeveloped latent print (fingermark) exposed to blood and later developed by enhancement with blood reagents such as amido black (AB) or leucocrystal violet (LCV) could appear as a genuine blood mark. We examined three different experimental conditions. In Experiment I, fingermark residue only was tested, as a control to confirm that fingermark residue alone does not react with the blood reagents AB and LCV. Experiment II investigated whether latent fingermarks exposed to blood dilutions could be treated with AB or LCV and subsequently appear as a genuine blood mark enhanced with AB or LCV. Experiment III tested whether latent fingermarks exposed to whole blood could be processed with AB or LCV and subsequently appear as a genuine blood mark enhanced with AB or LCV.The present study found that indeed, fingermark residue alone does not react with the blood reagents AB and LCV. In Experiment II, an interaction occurred between the fingermark residue and the diluted blood that caused the ridges to appear a red color. In the present study, this interaction is called a faux blood mark. While the faux blood mark phenomenon occurred most often following exposure to diluted blood, it did not occur consistently, and a predictable pattern could not be established. However, the reaction occurred more frequently following extended fingermark residue drying times. Faux blood marks are distinguishable from genuine blood marks prior to enhancement with blood reagents. Following treatment with blood reagents, it became increasingly difficult to determine whether the enhanced mark was a genuine blood print or a latent fingermark exposed to diluted blood. Latent fingermarks exposed to whole blood often resulted in a void prior to enhancement, but following treatment with blood reagents, were difficult to distinguish from a genuine blood mark enhanced with blood reagents.