Dating of Seals Produced with Stamp‐Pad Ink Using Gas Chromatography Method

Seals are often placed on important documents, and determining the date when a seal was affixed can be important to assess the authenticity of a document. In this study, thirty‐seven different brands of stamp‐pad inks and three different types of paper were used to make diachronic samples of the seals. The volatile components of stamp‐pad ink were determined, and the stamp‐pad ink was classified by gas chromatography with a flame ionization detector. Calibration curves were created to show the relationship between the content of volatile stamp‐pad ink components and the age of stamp‐pad ink entries stored under natural aging, UV‐induced aging, and heating aging conditions. The experimental results showed that GC was useful in the analysis of stamp‐pad ink and applicable for determining the relative age of stamp‐pad ink entries in some cases where the seal was placed on the document within 3 months.     

Preliminary Studies on the Absorbance Ratio Method Used to Determining the Age of Stamp‐pad Ink Seal

Stamp‐pad ink seals are often placed on important documents, and determining the dating of stamp‐pad ink seal is important to assess the authenticity of a document. In this study, 20 different brands and types of stamp‐pad inks were classified by ultraviolet visible spectrophotometer. Six different brands and types of papers were classified by micro‐Fourier transform infrared spectrometer and visual spectral comparator 6000. Three different brands of stamp‐pad inks and two different types of paper were used to make diachronic samples of the seals. A method was employed to date the stamp‐pad seals by comparing absorbance ratios and inks of known age. Curves were created to show the relationship between the absorbance ratio of ink and the age of the seals. The experimental results showed that the absorbance ratio method was applicable for the relative dating of stamp‐pad ink seals in some cases where the seal was placed on the document within 10 weeks.     

Prepared Disappearing Ink and Deciphering of Documents

Disappearing inks can be used for forgeries in many fields. In this study, thymolphthalein indicator solution was prepared as a disappearing ink. A total of 54 different solutions containing thymolphthalein were prepared at six different concentrations and nine different pH values. Among the prepared solutions, 0.16 g/50 mL and 0.32 g/65 mL thymolphthalein at pH 14 were the optimum solutions that were not distinguishable from regular ink when applied to promissory note. Fountain pens were filled with the abovementioned ink solutions and applied to promissory notes for experimental purposes. After 40 h, ink residues were not visible on promissory notes written with the ink with the optimum pH (pH = 14) value. To decipher the entries that disappeared, an instrumental method (Video Spectral Comparator‐8000) and a chemical method (using NH₃ vapor) were used, succeeded at 0.32 g/65 mL, but failed at 0.16 g/50 mL thymolphthalein. Therefore, NH₃ had to be sprayed for 0.16 g/50 mL with negligible harm.     

GC Analysis of Black Gel Pen Ink Stored under Different Conditions

In many criminal and civil cases in China, the most commonly questioned documents are those written with gel pen ink. An important task for forensic document examiners is to identify whether two or more ink entries in one or more documents were written with the same ink type. The identification of the age of gel ink entries made poses an important and difficult problem for forensic document examiners. In this paper, the volatile components of gel ink were determined and the gel ink was classified by gas chromatography with a flame ionization detector. Calibration curves were created to express the relationship between the content of volatile gel ink components and the age of gel ink entries stored under natural and UV‐induced aging conditions. The correspondence between the natural and UV‐induced aging conditions was also established. The experimental results showed that GC was useful in the analysis of black gel ink and applicable for determining the relative age of gel ink entries under certain conditions.     

Dating of Inkpad Seals Using the Extraction Rate Method: Preliminary Findings

Inkpad seals are often placed on important documents, and determining the date when a seal was affixed can be important to assess the authenticity of a document. In this study, three different brands of inkpads and four different types of paper were used to make diachronic samples of the seals. A double‐solvent extraction method was employed to date the inkpad seals by comparing extraction rates with inks of known age. Cyclohexane was selected as a weak solvent, and chlorobenzene was selected as a strong solvent. After testing, curves were created to show the relationship between the extraction percentage of ink and the date of the seals. The experimental results showed that the extraction rate method was applicable for the relative dating of inkpad seals in some cases where the seal was placed on the document within 6 months.     

Characterization of Printing Inks Using DART‐Q‐TOF‐MS and Attenuated Total Reflectance (ATR) FTIR

The rise in improved and widely accessible printing technology has resulted in an interest to develop rapid and minimally destructive chemical analytical techniques that can characterize printing inks for forensic document analysis. Chemical characterization of printing inks allows for both discrimination of inks originating from different sources and the association of inks originating from the same source. Direct analysis in real‐time mass spectrometry (DART‐MS) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR‐FTIR) were used in tandem to analyze four different classes of printing inks: inkjets, toners, offset, and intaglio. A total of 319 samples or ~ 80 samples from each class were analyzed directly on a paper substrate using the two methods. DART‐MS was found to characterize the semi‐volatile polymeric vehicle components, while ATR‐FTIR provided chemical information associated with the bulk components of these inks. Complimentary data results in improved discrimination when both techniques are used in succession resulting in >96% discrimination for all toners, 95% for all inkjets, >92% for all offset, and >54% for all intaglio inks.     

A Novel Forensic Tool for the Characterization and Comparison of Printing Ink Evidence: Development and Evaluation of a Searchable Database Using Data Fusion of Spectrochemical Methods

A searchable printing ink database was designed and validated as a tool to improve the chemical information gathered from the analysis of ink evidence. The database contains 319 samples from printing sources that represent some of the global diversity in toner, inkjet, offset, and intaglio inks. Five analytical methods were used to generate data to populate the searchable database including FTIR, SEM‐EDS, LA‐ICP‐MS, DART‐MS, and Py‐GC‐MS. The search algorithm based on partial least‐squares discriminant analysis generates a similarity “score” used for the association between similar samples. The performance of a particular analytical method to associate similar inks was found to be dependent on the ink type with LA‐ICP‐MS performing best, followed by SEM‐EDS and DART‐MS methods, while FTIR and Py‐GC‐MS were less useful in association but were still useful for classification purposes. Data fusion of data collected from two complementary methods (i.e., LA‐ICP‐MS and DART‐MS) improves the classification and association of similar inks.     

Evaluation of the Forensic Utility of Scanning Electron Microscopy‐Energy Dispersive Spectroscopy and Laser Ablation‐Inductively Coupled Plasma‐Mass Spectrometry for Printing Ink Examinations

Improvements in printing technology have exacerbated the problem of document counterfeiting, prompting the need for analytical techniques that better characterize inks for forensic analysis and comparisons. In this study, 319 printing inks (toner, inkjet, offset, and Intaglio) were analyzed directly on the paper substrate using scanning electron microscopy‐energy dispersive spectroscopy (SEM‐EDS) and Laser Ablation‐Inductively Coupled Plasma‐Mass Spectrometry (LA‐ICP‐MS). As anticipated, the high sensitivity of LA‐ICP‐MS pairwise comparisons resulted in excellent discrimination (average of ~ 99.6%) between different ink samples from each of the four ink types and almost 100% correct associations between ink samples known to originate from the same source. SEM‐EDS analysis also resulted in very good discrimination for different toner and intaglio inks (>97%) and 100% correct association for samples from the same source. SEM‐EDS provided complementary information to LA‐ICP‐MS for certain ink types but showed limited utility for the discrimination of inkjet and offset inks.     

In situ Study on the Diffusion Kinetics of Seal Ink by Microinfrared Spectroscopy

In document examination, it is of great importance to determine the composition of seal ink with different imprint times, and spectroscopic methods are widely used today. In this research, the diffusion of seal inks from three different brands on the same type of paper is monitored in situ by microinfrared spectroscopy and microinfrared imaging technology. The area of the absorption peak at 1743 cm^?1 gradually decreases with increasing diffusion time. The diffusion kinetics of seal ink on paper are also studied by analyzing the infrared spectra of seal inks at the same measuring point with different diffusion times. The research provides a basic study in understanding the diffusion behavior of seal ink on paper over short time spans.     

Considerations on the ASTM Standards 1789‐04 and 1422‐05 on the Forensic Examination of Ink

Abstract: The ASTM standards on Writing Ink Identification (ASTM 1789‐04) and on Writing Ink Comparison (ASTM 1422‐05) are the most up‐to‐date guidelines that have been published on the forensic analysis of ink. The aim of these documents is to cover most aspects of the forensic analysis of ink evidence, from the analysis of ink samples, the comparison of the analytical profile of these samples (with the aim to differentiate them or not), through to the interpretation of the result of the examination of these samples in a forensic context. Significant evolutions in the technology available to forensic scientists, in the quality assurance requirements brought onto them, and in the understanding of frameworks to interpret forensic evidence have been made in recent years. This article reviews the two standards in the light of these evolutions and proposes some practical improvements in terms of the standardization of the analyses, the comparison of ink samples, and the interpretation of ink examination. Some of these suggestions have already been included in a DHS funded project aimed at creating a digital ink library for the United States Secret Service.     

The Classification of Inkjet Inks Using AccuTOF™ DART™ (Direct Analysis in Real Time) Mass Spectrometry—A Preliminary Study

A novel approach for the analysis of inkjet inks is being reported. A time‐of‐flight mass spectrometer, coupled with a Direct Analysis in Real Time (DART?) ion source (AccuTOF? DART?), was used to determine if inkjet inks from various manufacturers and models of printers could be reliably differentiated, characterized, and identified. A total of 217 ink standards were analyzed. As inkjet printing often involves the use of multiple colors (e.g., cyan, magenta, yellow, and black) to form an image or text, two different approaches to creating a library of standards and sampling methods were evaluated for implementation in a standard operating procedure. This research will show that a microscopic examination of the region of interest is requisite to identify what colors were utilized during the printing process, prior to comparing with known standards. Finally, blind testing was administered with 10 unknown samples to assess the validity and accuracy of the methodology.     

Ink Dating Using Thermal Desorption and Gas Chromatography/Mass Spectrometry: Comparison of Results Obtained in Two Laboratories

An ink dating method based on solvent analysis was recently developed using thermal desorption followed by gas chromatography/mass spectrometry (GC/MS) and is currently implemented in several forensic laboratories. The main aims of this work were to implement this method in a new laboratory to evaluate whether results were comparable at three levels: (i) validation criteria, (ii) aging curves, and (iii) results interpretation. While the results were indeed comparable in terms of validation, the method proved to be very sensitive to maintenances. Moreover, the aging curves were influenced by ink composition, as well as storage conditions (particularly when the samples were not stored in “normal” room conditions). Finally, as current interpretation models showed limitations, an alternative model based on slope calculation was proposed. However, in the future, a probabilistic approach may represent a better solution to deal with ink sample inhomogeneity.     

Modeling Bone Surface Morphology: A Fully Quantitative Method for Age‐at‐Death Estimation Using the Pubic Symphysis

The pubic symphysis is widely used in age estimation for the adult skeleton. Standard practice requires the visual comparison of surface morphology against criteria representing predefined phases and the estimation of case‐specific age from an age range associated with the chosen phase. Known problems of method and observer error necessitate alternative tools to quantify age‐related change in pubic morphology. This paper presents an objective, fully quantitative method for estimating age‐at‐death from the skeleton, which exploits a variance‐based score of surface complexity computed from vertices obtained from a scanner sampling the pubic symphysis. For laser scans from 41 modern American male skeletons, this method produces results that are significantly associated with known age‐at‐death (RMSE = 17.15 years). Chronological age is predicted, therefore, equally well, if not, better, with this robust, objective, and fully quantitative method than with prevailing phase‐aging systems. This method contributes to forensic casework by responding to medico‐legal expectations for evidence standards.     

The Utility of the Samworth and Gowland Age‐at‐Death “Look‐up” Tables in Forensic Anthropology*

Abstract: Accurate age‐at‐death estimates are crucial to forensic anthropologists when onstructing biological profiles aimed at narrowing a missing‐persons list and to allow for timely and efficient identification of an unknown victim. The present contribution evaluates the utility of three new age‐at‐death estimation techniques recently proposed by Samworth and Gowland (2007). Results indicate that, in the samples under study, the Samworth and Gowland estimates from the pubic symphysis and auricular surface perform similar to alternate phase methods. The combined method does not appear to further enhance either the precision or the accuracy of the single pubic symphysis age‐at‐death estimate. In conclusion, these new methods seem to be more robust to distribution deviations than originally proposed by Samworth and Gowland (2007). They are therefore suitable for immediate and reliable forensic usage in the United States and worthy of further research for their use in North American forensic contexts.     

TOF‐SIMS Analysis of Red Color Inks of Writing and Printing Tools on Questioned Documents

Time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) is a well‐established surface technique that provides both elemental and molecular information from several monolayers of a sample surface while also allowing depth profiling or image mapping to be performed. Static TOF‐SIMS with improved performances has expanded the application of TOF‐SIMS to the study of a variety of organic, polymeric, biological, archaeological, and forensic materials. In forensic investigation, the use of a minimal sample for the analysis is preferable. Although the TOF‐SIMS technique is destructive, the probing beams have microsized diameters so that only small portion of the questioned sample is necessary for the analysis, leaving the rest available for other analyses. In this study, TOF‐SIMS and attenuated total reflectance Fourier transform infrared (ATR‐FTIR) were applied to the analysis of several different pen inks, red sealing inks, and printed patterns on paper. The overlapping areas of ballpoint pen writing, red seal stamping, and laser printing in a document were investigated to identify the sequence of recording. The sequence relations for various cases were determined from the TOF‐SIMS mapping image and the depth profile. TOF‐SIMS images were also used to investigate numbers or characters altered with two different red pens. TOF‐SIMS was successfully used to determine the sequence of intersecting lines and the forged numbers on the paper.     

The use of filtered light for the evaluation of writing inks analyzed using thin layer chromatography

Thin layer chromatography (TLC) is a scientific methodology that can be used to compare and characterize ink formulations. Occasionally, when evaluating chromatographic profiles on a TLC plate with ambient light, different ink formulations, or the same inks from different batches, may appear indistinguishable. The use of filtered light can be very effective to illuminate characteristics that are not readily apparent with ambient light. There are a diverse number of components commonly found in writing inks, and it may be that some of them respond to particular wavelengths of energy that are not visible to the unaided eye (i.e., colorless). There has been very little information published that addresses the use of filtered light for evaluating TLC plates. Twenty-nine ballpoint writing ink samples were selected for TLC analysis. Further evaluation using an alternate light source, coupled with the appropriate filter, proved to be an effective means for definitive discrimination in some cases.     

Testing Reliability of the Computational Age‐At‐Death Estimation Methods between Five Observers Using Three‐Dimensional Image Data of the Pubic Symphysis,

In an effort to standardize data collection and analysis in age estimation, a series of computational methods utilizing high‐dimensional image data of the age indicator have recently been proposed as an alternative to subjective visual, trait‐to‐phase matching techniques. To systematically quantify the reproducibility of such methods, we investigate the intrascan variability and within‐ and between‐observer reliability in initial scan data capturing and editing using 3D laser scans of the Suchey–Brooks pubic symphysis casts and five shape‐based computational methods. Our results show that (i) five observers with various training background and experience levels edited the scans consistently for all three trials and the derived shape measures and age estimates were in excellent agreement among observers, and (ii) the computational methods are robust to a measured degree of scan trimming error. This study supports the application of computational methods to 3D laser scanned images for reliable age‐at‐death estimation, with reduced subjectivity.     

A Four‐Stage Method of Age at Death Estimation for Use in the Subadult Rib Cortex*,†

Abstract: Age estimation in the subadult skeleton can be rather precise when the epiphyses and dentition are present, but incomplete or commingled remains still present a challenge. Histomorphometric age‐at‐death estimation methods developed for use on adults are based on the age‐associated accumulation of osteons. In the growing skeleton, there is a poor correlation between osteon numbers and age until the latter half of the second decade. As a result, there has been no histological aging method for use in subadults. The analysis of the rib cortex of 72 subadults ranging in age from 2 to 21 years has identified a series of developmental changes in the bone microstructure that can be used to estimate age. This qualitative method utilizes the systematic changes in rib cortical morphology to classify ribs into one of four age phases. This method can be applied to immature skeletons in forensic, archaeological, and paleontological contexts.     

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.