激光雕刻法伪造印章印文的检验技巧

激光雕刻技术是当代激光技术、电脑技术、精密数控技术、电子技术等的结合,是光、机、电一体化的一种刻印技术,大大提高了印章刻制的丁艺水平和制作速度,已被社会广泛应用.同时,用激光雕刻法伪造印章印文的案件也不断出现,且达到真假难辨的程度,对此类案件的鉴定是文检人员面临的一个难题,需要不断地总结和更新检验方法.     

Stability and Specificity of Counterfeit Protection System Code

In this study, the stability and specificity of a counterfeit protection system (CPS) code were determined. This research involved an analysis of a counterfeit protection system code unit over time using the pattern location measurement method. We collected 379 sample sheets from 196 printers or photocopiers, covering 14 original brands, including 129 models. There was an interval of at least two months between the collections of samples from each machine. Four types of characteristics were established: CPS pattern unit, distance of the CPS unit, position of dots, size and shape of the dot. Except for the partial changes in the Xerox brand, no other brand exhibited changes over time. This implies that the CPS characteristics are stable. Meanwhile, no correlation was noted between the combinations of the characteristic systems in the collected samples, which implied strong specificity.     

Determination of the Sequence of Intersecting Lines Between Toners and Seals by Laser Fluorescence Microscope

Fluorescence microscope is considered to be one of the most effective ways to examine the sequence of intersecting seal and toner lines of questioned documents. In reality, however, the toner (mainly divided into compact and noncompact toners) and seal of a questioned document have such a complex morphology and sequence of crossing lines that current methods cannot meet the requirement of practical document identification. In view of the challenges of document examination, a laser fluorescence microscope and method are developed in this study. The developed microscope provides additional functionality to traditional fluorescence microscopes of transmitted light modality, laser excitation, selectable excitation wavelength, and selectable fluorescence filters. The results obtained from the method of comparisons between transmitted light and fluorescence modalities were positive under most conditions, particularly for noncompact toner examination for which a 100% accuracy rate and 90% detection rate were achieved in blind testing.     

Application of 3D Laser Scanner to Forensic Engineering

In the case of building collapses and overturned structures, a three‐dimensional (3D) collapse or overturn model is required to reconstruct the accident. As construction sites become increasingly complex and large, 3D laser scanning is sometimes the best tool to accurately document and store the site conditions. This case report presents one case of a structure collapse and one case of an overturned crane reconstructed by a 3D laser scanner. In the case of structural collapse of a prefabricated shoring system, a 3D model reconstructed all the members successfully, a task that is nearly impossible using a scale such as a tape measure. The reconstructed prefabricated shoring system was verified through a structural analysis through comparison with the construction drawings to investigate faults in construction. In the case of the overturned crane, the jib angle and other major dimensions were successfully acquired through 3D laser scanning and used to estimate the working radius. As a result, the propriety of the working radius with the given lifting load was successfully determined.     

Establishment of 43-plex SNP Typing System and Its Forensic ApplicationCSCD

Objective: To evaluate the application of 43 -plex SNP typing system in forensic science. Methods: The typing of 43 SNP loci in 123 unrelated Han individuals from East China was detected by MALDI-TOF-MS. The application value of 43-plex SNP typing system was assessed according to the forensic parameters of population genetics. Results: All the 43 SNP loci of 123 individuals showed no significant departure from Hardy-Weinberg equilibrium (P>0.05). Excepted rs1355366, rs2270529, rs10776839 and rs938283, there were 39 SNP loci had minor allele frequencies (MAF), which were greater than 0.25. Among the 25 loci MAFs, 24 ranged from 0.4 to 0.5, while 3 were close to 0.4. The DP, CDP, PIC, Ho, PEtrio and PEduo of the 43 SNP loci were 0.290 1-0.654 4, 1-9.8×10-11, 0.170 8-0.500 0, 0.155 7-0.593 5, 0.085 4-0.250 0 and 0.014 6-0.125 0, respectively. The CPEtrio and CPEduo were 0.999 986 and 0.992 436 1, respectively. Conclusion: The 43-plex SNP typing system in present study shows a high polymorphism, which can be an effective supplement and verification for traditional STR genetic markers. It also can be used with other commercial kits for the forensic paternity testing and individual identification. © 2018 by the Editorial Department of Journal of Forensic Medicine.     

Application of Raman Spectroscopy and Surface‐Enhanced Raman Scattering to the Analysis of Synthetic Dyes Found in Ballpoint Pen Inks*

Abstract: The applicability of Raman spectroscopy and surface‐enhanced Raman scattering (SERS) to the analysis of synthetic dyes commonly found in ballpoint inks was investigated in a comparative study. Spectra of 10 dyes were obtained using a dispersive system (633 nm, 785 nm lasers) and a Fourier transform system (1064 nm laser) under different analytical conditions (e.g., powdered pigments, solutions, thin layer chromatography [TLC] spots). While high fluorescence background and poor spectral quality often characterized the normal Raman spectra of the dyes studied, SERS was found to be generally helpful. Additionally, dye standards and a single ballpoint ink were developed on a TLC plate following a typical ink analysis procedure. SERS spectra were successfully collected directly from the TLC plate, thus demonstrating a possible forensic application for the technique.     

Evaluation of Four Fingerprint Development Methods for Touch Chemistry Using Matrix‐Assisted Laser Desorption Ionization/Time‐of‐Flight Mass Spectrometry,

Four preparation techniques for MALDI/TOF mass spectrometry were compared to determine the ability to gather intelligence for investigations through the chemical analysis of latent fingerprints, defined as “touch chemistry.” Compatible fingerprint development processes used for identification along with new techniques are necessary to evaluate touch chemistry. Ten volunteers deposited fingerprints from solvent residues containing drugs and explosives onto microscope slides. The developers included (A) fingerprint powder, (B) MALDI matrix, (C) fingerprint powder and lifting, and (D) cyanoacrylate fuming with fingerprint powder. Qualitative identification was based on ion images and spectra. The highest average detection rates (88%) were found using methods A and B. Methods C (52%) or D (18%) had limited success. Results demonstrate the importance of imaging coupled to extracted mass spectral data in detecting analytes in deposited fingerprints. Overall, the results suggest continued development of touch chemistry applications could prove useful for gathering intelligence and forensically relevant information.     

死后离体人肝组织的激光共聚焦显微拉曼光谱分析

目的观察和探讨人死后肝组织细胞激光共聚焦显微拉曼光谱的变化规律及其与死亡时间的关系。方法离体肝组织于死后48～72h内每隔4h提取样品,采用激光共聚焦显微拉曼光谱技术进行检测。观察800cm-1～3 200cm-1范围内检测样本特征峰的变化,指认其对应的化学基团,选择强度比值I1094/I2923作为响应值,并进行统计学计算。结果在48～72h内,随时间的延长,肝组织细胞主要散射峰峰位无明显变化,而其峰强度有明显差异;与核酸有关的峰（1 094cm-1）强度随时间推移有明显下降;与脂类有关的峰（1 454cm-1、2 923cm-1）强度变化不明显;各相对峰强（I1094/I2923）随死亡时间的推移而减小,并得到回归方程（r=0.914）。结论人死后肝组织细胞DNA降解随死亡时间延长呈下降趋势,I1094/I2923值与PMI呈负线性关系。激光共聚焦显微拉曼光谱技术有望成为推断死亡时间的检测方法。     

无交叉笔画状态下激光打印文字与中性笔书写文字形成时序的实验研究

目的探索无交叉笔画状态下激光打印文字与中性笔书写文字的时序特征及变化规律,以求运用于案件检验。方法以两种不同时序,请5名志愿者分别执不同中性笔在120张A4纸张上书写文字,并使用4台不同型号激光打印机打印文字,再运用奥博视频层晰显微镜对实验样本进行放大观察。结果证实在两种时序条件下制作的实验样本之间存在诸多差异性特征。结论这些差异性特征为准确判定无交叉笔画状态下激光打印文字与中性笔书写文字的时序提供了基础实验依据。     

Visualization of latent fingerprints using fluorescence lifetime imaging on paper emitting strong fluorescence

Latent fingerprints were successfully visualized using fluorescence lifetime imaging (FLIM) on paper which emits strong fluorescence with a lifetime close to that of fingerprints and thus from which it is difficult for time-resolved spectroscopy to visualize fingerprints. Latent fingerprint samples on paper were excited using a 450 nm or 532 nm nanosecond pulsed-laser, and time-resolved fluorescence images were obtained at a delay time of 6–16 ns in intervals of 1 ns, to the excitation pulse. The excitation beam was expanded using a lens, and the fluorescence from the fingerprints was captured using an intensified CCD camera. Because of the large fluorescence intensity of the background paper of approximately two to four orders of magnitude larger than that of the fingerprint, the fingerprint was not visualized on each fluorescence image by time-resolved spectroscopy. However, the fingerprint was visualized in a FLIM image constructed using a series of the fluorescence images for the case with the fluorescence intensity of the background paper being four orders of magnitude larger than that of the fingerprint. The difference in fluorescence lifetime in the FLIM image of the visualized fingerprint and background paper was in the order of 0.1 ns, which was an order of magnitude smaller than the inherent fluorescence lifetime of a few nanoseconds for the fingerprints and paper. It was demonstrated that, at a background fluorescence intensity with a certain order of magnitude larger than that of fingerprints, FLIM has the potential to visualize latent fingerprints which cannot be visualized by time-resolved spectroscopy.