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The handwriting characteristics of machine imitative signature in terms of writing style, layout, writing method are almost completely consistent with the imitated signature. A general analysis of the differences between machine imitative signatures and handwritten signatures in terms of various handwriting features makes little sense. On the contrary, there are more detailed differences on some handwriting characteristic like writing strength, writing speed and so on. In this experiment, the characteristics of stroke mark are taken as the research object, and the samples of human handwritten signatures are collected and the corresponding machine imitative signatures are made. The similarities and differences between them in stroke marks are observed and summarized by microscope. The results show that there are morphological differences between machine imitative signature and handwritten signature in ink dots, indentations, stroke width and thickness and so on. Machine-writing has strong repeatability and similarity in these features, and the same features always appear in other handwriting. Because of the different structure and function of the writing robot, the writing characteristics of the machine itself also affect the stroke characteristics of the machine imitative signature. For example, ink and white line features are not observed in machine imitative handwriting. In conclusion, the stroke marks of machine imitative signature have strong regularity and high similarity, while the stroke marks of handwritten signatures have strong randomness and rich changes. Affected by machine itself, the machine imitative signature and the human writing signature have obvious and fixed differences in stroke mark. It is a feasible handwriting inspection idea to identify machine-writting handwriting from the perspective of stroke mark.
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In order to improve the development effect of latent blood fingerprint, this paper attempts to introduce fluorescent labeling technology into latent blood fingerprint development. By taking advantage of the characteristics of strong esterification activity of N-hydroxy-succinimide ester, easy reaction with the amino group of protein to form amide chemical bond and stable structure, a new fluorescence derivative 5-carboxyfluorescein-N-hydroxy-succinimide ester (CFSE) was synthesized and applied to latent blood fingerprint development area for the first time. In this paper, the developing ability of CFSE on latent blood fingerprint will be systematically explored. By setting a series of gradients, using comparative experiments, hypothesis testing and other methods, the operation method and optimal reagent formula of the fluorescein to develop latent blood fingerprints were determined. CFSE can be widely used in the development of latent blood fingerprints on non-permeable complex backgrounds and dark background objects, and has little effect on sample DNA extraction, and compared with acid yellow, the results showed that the fineness of the lines and the contrast with the background were higher. In addition, the study also determined the order of using CFSE in combination with the common methods for developing latent blood fingerprints. CFSE has the advantages of strong fluorescence brightness, high fineness, obvious contrast with the background, less fluorescence stains, and easy washing, and the overall effect is better, which provides a new method for latent blood fingerprints development.
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Forensic SNP genealogy can infer distant kinship based on SNP chip data. In order to clarify the ability of genealogical inference technology based on SNP chip data to detect trace DNA in forensic field, in this study Illumina CGA microarray was used to detect the samples. The samples were preliminarily evaluated based on the DNA input, detection rate, sample heterozygosity and other indicators, then the IBS and IBD algorithms were used for forensic SNP genealogy. The classification consistency was compared with the reference samples, and the factors affecting the prediction accuracy were analyzed, the detection ability of the technology system for different input amounts of DNA were determined, and finally the accurate SNP typing data in the low-quality data were screened based on the signal ratio and other indicators, so as to improve the use value of the trace DNA detection data. The results show that when the DNA input was higher than 1.95 ng, the IBS algorithm had an average confidence interval accuracy of 94.33% and 91.96% for IBD, and when the input was 488－781 pg, the IBS algorithm had an accuracy of 23.11% for the average confidence interval for 1－5 kinship, while the IBD algorithm reached 30.13%. When the DNA input is less than 488 pg, both the IBS and IBD algorithms are unable to make genealogical inferences. Allele insertion is a major factor affecting the accuracy of pedigree inference, and when the homozygous error reaches 22.5%, the sample cannot be used for pedigree inference. By screening the signal ratio, the heterozygous SNP loci with a signal ratio greater than 1.5 can be removed, which can improve the genealogical inference ability of low-input samples. Based on the real family data of Illumina CGA chips, this study analyzed the influence of sample input on the accuracy of genealogical inference, and optimized the SNP data by signal ratio, so as to improve the application value of low-input samples in genealogical inference.
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In the practice of document examination, the number of cases involving the determination of crossing sequence of printed and written strokes is increasing year by year, but there is a lack of national and industry technical standards for the identification of cross-timing between printed strokes and handwriting. This study created crossed stroke samples formed by random combination of black inkjet printing devices (categorized into dye-based ink and pigment-based ink) and ballpoint pen with different brands and models in different orders, and a VF20 three-dimensional high-magnification video fluorescence microscope was used to examine those samples. Additionally, through the control variable method and the single variable method, the study investigated the effects of factors such as paper, time interval between two kinds of ink marks, writing cushion and printing mode on the determination results of the crossing sequence between inkjet printer ink and ballpoint pen ink. The results showed that when the ink from two types of inkjet printers and ballpoint pen intersect in the same crossing sequence, there were some differences in microscopic performances. And except the printing mode factor, other variables had no significant influence on the result judgment. Therefore, for different types of crossed stroke samples, sequencing the superimposed lines with black inkjet printing ink versus ballpoint pen ink by VF20 High Mag Fluorescence Microscope is feasible. This research can provide important reference for the examination of related cases, and meet the increasing demand for sequencing the intersections of printed strokes with handwriting.
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Laser printers are gaining popularity in everyday work and life, but they have also become a common tool for criminal activities. Traditional document inspectors have relied on color “tracking codes” to inspect color laser-printed documents. However, recent software developments that can remove these codes have posed new challenges for document inspection. This paper presents an experimental study on the mesh characteristics of color laser-printed documents, exploring the nuances of mesh morphology, spacing, area, and angle. The research was conducted on various brands and models of printers, and different image resolutions were selected for sample production. By observing and comparing the print dot characteristics of the same section, the study aimed to uncover the underlying patterns of mesh features in laser-printed documents. The research reveals that the dot characteristics of the same laser printer exhibit relative stability across different printing time. Moreover, when the same printer is used to print images of varying resolutions, the differences in screening characteristics are negligible. Conversely, distinct brands and models of printers yield diverse dot patterns, dot spacing, dot areas, and mesh angles. Notably, the dot pattern and mesh angle characteristics serve as highly valuable identifiers, particularly in the context of “same-machine” identification. This research underscores the feasibility of utilizing mesh features to differentiate laser-printed documents, thereby offering novel inspection strategies for the authentication of color laser-printed documents.
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The image ink of printed document is composed of halftone dot ink. Different manufacturers have configured different halftone algorithms for printing equipment, which makes the printed image have specific dot morphology. Two-dimensional fast Fourier transform (FFT) technology can transform the printed dot image from spatial domain to frequency domain, and obtain the spectral characteristics of dot ink. Therefore, spectral analysis can effectively assist in identifying the formation mode of the document. This paper selects 27 kinds of 32 toner printing equipment that are common in the market, and samples and analyzes the ink spectrum characteristics of images printed and copied by toner multifunctional printing equipment, focusing on the analysis of the ink spectrum characteristics of amplitude-modulated screen printing images, blue noise screen copying images and images with two sets of dots superimposed by copying and printing originals.The results show that two-dimensional FFT provides easy-to-identify ink spectrum characteristics, which can distinguish the ink morphology of images printed by different halftone algorithms, thus distinguishing between copied and printed images, and at the same time identifying the formation mode of copied manuscripts. In this paper, a method based on FFT technology is proposed to identify the ink formation mode of toner printing documents, which provides an objective and effective new method and basis for judging the document formation mode in document retrieval.
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To establish a high performance liquid chromatography-tandem hybrid triple-quadrupole linear ion trap mass-spectrometry method for qualitative and quantitative determination of etomidate in blood and hair. Deuterium cocaine was selected as the internal standard, and blood sample was extracted by acetonitrile (V/V, 1/6), then centrifuged at high speed; hair sample (about 20 mg) was ground by a ball mill, then extracted by methanol and passed through the organic membrane. Using 0.1% (V/V) formic acid aqueous solution and 0.1% (V/V) formic acid acetonitrile as mobile phase, the analyte was separated and analyzed by an ACQUITY UPLC®C18 (2.1 mm×100 mm×1.7 μm) column. Electrospray positive multiple reaction monitoring/information-dependent acquisition / enhanced product ion scanning (MRM-IDA-EPI) and secondary library retrieval were used for analysis. The results showed that etomidate in blood had a good linear relationship in the range of 1.0 to 100.0 ng/mL (r>0.995). The linear relationship of etomidate in hair was good in the range of 0.05 to 5.0 ng/mg (r>0.995). The detection limits (S/N≥3) for blood and hair were 0.2 ng/mL and 0.002 ng/mg, and the quantitative limits (S/N≥10) were 0.5 ng/mL and 0.005 ng/mg respectively. The recoveries of 1.0, 10.0, 100.0 ng/mL in spiked blood were 97.1% to 103.4%, and 0.5, 2.5, 5.0 ng/mg in spiked hair were 84.0% to 99.8%. The relative standard deviation was less than 15%. This method can be applied to the qualitative and quantitative analysis of etomidate in blood and hair in the juridical practice.
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In arson incidents, suspects may employ plastic items such as lighters and containers for accelerants as tools, which are prone to retaining fingerprint evidence. However, the high-temperature environment of a fire scene can cause plastics to undergo a series of changes including softening, deformation, melting, pyrolysis, and combustion, with the composition of fingerprints also being altered. Therefore, studying the evolution of the fingerprint-bearing substrate under high-temperature conditions holds significant importance for fingerprint development. This study focused on PET plastic mineral water bottles and ABS plastic lighter shells as research subjects. Initially, the thermal properties of these two plastic materials were analyzed to set the heating temperature and duration that simulate fire scene conditions. Subsequently, the latent fingerprints on the heated plastics were developed using the fluorescent powder method, and the evolution of the plastic substrate and fingerprint patterns was observed in real-time via a hot-stage microscope. The mechanism of how high temperature affect fingerprint development on the surfaces of thermoplastic plastics was explained in conjunction with the phase behavior of the substrate materials. The results indicate that the effectiveness of fingerprint development on thermoplastic surfaces is predominantly influenced by the intrinsic properties of the substrate. Before the pyrolysis of thermoplastic materials, the fluorescent powder method can effectively develop fingerprint, but the ridges will be noticeably distorted due to plastic softening, and the subsequent melting process further severely interferes with fingerprint comparison and identification. Specifically, the PET plastic bottle heated at 200 °C for 10 to 30 minutes can still exhibit fingerprint patterns, but prolonged heating exacerbates the distortion. When the temperature rises to 250 °C, the plastic bottle melts completely, rendering latent fingerprints invisible. For the ABS plastic lighter shell, fingerprint ridges can be revealed but are severely distorted at 250 °C; when the temperature reaches 300 °C, the lighter shell undergoes severe deformation, and fingerprints cannot be revealed. The results of this study provide invaluable scientific data to support fingerprint development on thermoplastic plastics under high-temperature fire scene conditions.
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To evaluate the effect of 10% unbuffered formalin fixation time on STR detection of human skeleton, in the paper five skeletons were selected, and the backbone segments were divided into 12 segments using a chainsaw. The backbone segments were soaked in a 10% unbuffered formalin solution at room temperature, and samples were taken at various time intervals. DNA was quantified using QuantiFiler® Trio DNA Quantification Kit. PCR amplification was performed using IDentifier DNA typing kit (Yanhuang 34) and SureID®X37 Human X-STR kit, and STR data was obtained using 3500xL genetic analyzer. The results showed that fixation time of skeletons was inversely proportional to the DNA mass concentration and proportional to the DNA degradation index. Full STR profile could be obtained by autosomal and X chromosome tests on skeletons fixed within 10 days in 10% unbuffered formalin. For samples fixed for a period of 22 days, the STR detection rate could be maintained above 77.33%. When the fixed time was extended to 30 days, the allele detection rate of samples was significantly reduced to less than 30%. Finally, when the fixed time had reached 60 days, the DNA quantitative results in all samples dropped below 0.02 ng/µL, and only a few samples yielded sporadic STR genotypes for small fragments. In conclusion, the fixation time in 10% unbuffered formalin affects DNA quality extracted from human skeletons and is thus an important factor affecting the STR detection rate.
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Blood stains serve as crucial evidence aiding investigators in solving cases, linking suspects to crimes, and reconstructing crime scenes. Criminals frequently attempt to remove blood stains from clothing through washing, potentially altering or eliminating stained areas, thereby complicating investigators’ efforts to locate and extract these stains. To uncover the optimal method for detecting blood stains on laundry, enhance the accessibility of physical evidence, and provide robust evidence for criminal case detection and court sentencing, this study evaluates the effectiveness of amino black 10B, acid yellow reagent, luminol, tetramethylbenzidine, and a 415 nm light source in revealing latent bloodstains on cotton, cotton-polyester blends, and polyester textiles in both dark and light hues, following washes with enzyme-containing and enzyme-free detergents. For occult blood traces on washed light-colored polyester-cotton blend and polyester textiles, the apparent effectiveness ranked in descending order was: luminol, amino black 10B, acid yellow reagent, 415 nm band light source, and tetramethylbenzidine. For light-colored cotton textiles, the order was luminol, amino black 10B, 415 nm band light source, and acid yellow reagent. For dark-colored cotton, polyester-cotton blend, and polyester textiles, both luminol and acid yellow reagent exhibited good results, with luminol demonstrating superior performance. In conclusion, luminol reagent has proven to be exceptional in revealing occult blood traces on washed textiles, which is of paramount importance in solving crimes.
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With the advancement of paperless offices, handwritten electronic signatures have become widely adopted across various sectors, including banking, government affairs, and commerce. These signatures refer to the textual impressions created by fingers or stylus pens on electronic screens, such as smartphones and digital tablets. Concurrently, dynamic attributes like writing duration, stroke sequence, and pen pressure are captured and stored electronically on computers. From an implementation perspective, handwritten electronic signatures fall within the broader category of electronic signatures. However, they differ from digital signatures in terms of implementation technology, presentation format, verification methods, and technological requirements. Given the distinct verification methodologies, handwritten electronic signatures should not be subject to the authentication framework outlined in The Electronic Signature Law. Instead, their unique handwritten characteristics should be analyzed from a morphological angle. Nevertheless, shifts in writing devices and mediums have diminished certain static characteristics, often resulting in imperfections in the identification process. This complexity is further compounded by difficulties in leveraging dynamic features for identification, challenges in distinguishing copied and pasted handwriting, and a scarcity of experienced authenticators. Consequently, during the identification process, it is crucial to: collect comparable original specimens, specify the writing devices used, gather samples from identical or similar sources as the specimens, and utilize identification expertise to identify stable traits with individual variations. By adopting a comprehensive quantitative analysis approach and corroborating with electronic data, the accuracy of identification conclusions can be significantly enhanced.
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Hair matrix reference material is a class of reference material in which the target substance is combined with the biological matrix of hair and the concentration of the target substance is determined. Hair matrix reference material has a higher consistency with the real case samples involved in the field of forensic toxicology, reducing errors in calibration and validation by using this material during sample pre-treatment and instrument detection processes, thereby enhancing the accuracy and reproducibility of detection data, and its application has a positive effect on improving the testing ability of laboratories, advancing scientific and technological progress in the field of forensic toxicology, and enhancing judicial impartiality. This paper focuses on the hair matrix samples which are commonly analyzed in forensic toxicology, specifically addresses the structure of hair, the mechanism through which drug are incorporated into the hair, main preparation methods of hair matrix reference material, and provided a comprehensive evaluation of theoretical basis and development status of hair matrix reference materials for analysis in forensic toxicology. It is intended to serve as a reference for the development and application of hair matrix reference material.
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Obtaining a single male DNA profile from aged mixed stains composed of sperm and vaginal epithelial cells, which are common challenging forensic biological materials, is difficult due to severe cell degradation and trace sperm content. This paper presents the testing process and successful experience of a sexual assault case, providing a promising solution for handling aged mixed stains with limited sperm content in practical scenarios. The sample was a vaginal swab from the victim, which yielded an unidentified single male DNA profile by DNA analysis in 2004. In the identification process in 2023, the PSA test on the sample was confirmed to be positive. Only the supernatant part yielded a single female DNA profile and an incomplete Y-STR profile using the conventional differential lysis method, and no DNA was detected in the precipitate part. In contrast, by utilizing commercial immunomagnetic bead kits and optimized experimental procedures, sperm cells were successfully isolated from the seminal and vaginal mixed-stain samples under enhanced incubation conditions, resulting in the acquisition of a single male DNA profile. At the end of this paper, the application value and precautions of the method for sperm cell separation based on immunomagnetic beads in the analysis of mixed stains are discussed.
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As technology advances, mobile device forensics becomes increasingly challenging in the context of constantly updated operating systems and enhanced data encryption techniques. This paper, taking the TikTok application data extraction from a Huawei mobile phone in an actual case as an example, delves into the difficulty of extracting data from specific applications in new Android phones. To tackle this challenge, this study proposes a method utilizing a root-privileged phone to clone data from the source device and subsequently extract the required information, thereby achieving successful data retrieval. Furthermore, recognizing the inefficiencies and time-consuming nature of traditional manual timestamp conversion methods during targeted database analysis, this study has developed a novel database retrieval tool. This tool automates the process of swiftly retrieving and analyzing data from key time periods across multiple databases within a predefined directory, significantly enhancing processing speed and efficiency. Thus, our study not only offers a solution to the challenges of data extraction and analysis but also serves as a valuable methodological reference for mobile device forensics in similar cases.
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The stapes, the smallest bone in the auditory ossicles, has its head connected to the anvil bone by a ligament, while its base seals the vestibular window. Simple stapes fractures caused by trauma are uncommon and can result from direct or indirect forces, such as tympanic muscle contraction, airflow, and lymphatic impingement. A male victim sustained blunt force to the head, chest, and abdomen. Clinical examination and surgical revealed a displaced fracture of the stapes superstructure without concomitant temporal bone or other ear injuries, indicating an indirect trauma mechanism. Analyzing the injury mechanism proved challenging; however, based on the available evidence and relevant literature, the author proposed that the fracture likely resulted from shear forces generated by the combination of head trauma (from punching and subsequent falling), as well as contraction traction force of the sternocleidomastoid muscle. This analysis aims to provide forensic professionals with a reference for evaluating similar cases and assessing injury severity.
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The determination of vehicle speed in traffic accidents is a key factor in analyzing the accident process, clarifying responsibilities and cause. However, speed identification has also become challenging due to its reliance on precise on-site inspection data, technical complexity, and multiple uncertainties. This article explores the process of vehicle speed identification in a real car-pedestrian collision case, including formula selection, confirmation of collision contact point, and parameter validation. Telematics-box (T-box) data, video recordings, and simulation software were utilized to verify the vehicle speed, successfully correcting the initial assessment result. This article provides a practical reference for the accurate application of pedestrian throw distance formulas in car-pedestrian collision analysis.
