伪装笔迹实验样本的识别与提取技巧

笔迹样本的质量是关系笔迹鉴定工作成败的一个重要因素,本文即介绍了在实验样本中如何识别伪装笔迹,并针对具体情形提出了在笔迹实验样本收集与提取中应注意的事项及相关技巧,以期对笔迹鉴定工作能够有所裨益。     

案后样本笔迹特征的选取

在笔迹检验中，合适的样本是笔迹进行检验的基本要素，是能否进行鉴定的先决条件。其字迹收集的质量、数量的好坏直接影响着笔迹鉴定工作的顺利及鉴定结论的准确性。样本按时间分为案前样本及案后样本两种。案前样本即是在案件发生以前书写的，而案后样本则是指案件发生后，由嫌疑人亲笔书写的文字材料。有两种情况：一种是发案后嫌疑人日常工作、学习、生活中写的文字材料，在被确定为嫌疑对象后，收集起来作为笔迹样本；另一种是在侦破工作开始后，因一时找不到嫌疑人现成的笔迹样本，或已收集的样本不足，在不暴露意图的情况下，通过某种…     

笔迹检验中案后笔迹样本的收集和利用

在笔迹检验中，只要能收集到书写人的案前笔迹样本，一般均能完成检验的要求，但在有些案件中，收集案前笔迹样本比较困难，就需要利用案后笔迹样本进行检验。案后笔迹样本的收集通常采用让其所在单位组织统一的考试、开展问卷调查、撰写情况汇报和学习体会等形式进行，有时这些方法不一定奏效。笔者在工作实践中总结出两种案后笔迹样本的收集方法，介绍如下。     

案后文字样本的区分、使用

在笔迹检验案件中，一是用摹仿手段进行贪污冒领的经济案件日益增多，这类案件的特点就是检材字迹少，并且大都是人名用字，这些字在嫌疑人的样本材料中很少出现；二是在一部分笔迹案件中，嫌疑人样本字迹很少，特别是在一些待业青年、农村民工中，平时很少动笔写字，收集他们案前的样本字迹确实困难，因此利用案后文字样本材料进行检验，就是这类案件笔迹检验的一个特点。如果按以往习惯，“以案前样本笔迹做基础，以案后样本笔迹做参考”，就不利于这类案件的检验。在鉴定实践中，针对这类案件的特点，细致地分析案后样本笔迹，灵活地区分和运用，收到了较好的效果。     

浅谈笔迹样本的种类、条件及提取方法

笔迹样本是指由刑事案件的犯罪嫌疑人、被告人,民事、行政案件的当事人以及其他与案件有关联的人亲笔书写的,用来与检材笔迹物证上的字迹进行比较鉴别的字迹材料,是犯罪嫌疑人、当事人及关联人(以下均称嫌疑人)书写习惯特征的集中体现。因此,笔迹样本是否真实可靠、充分、具有可比性,直接关系到鉴定结论准确与否。侦查、调查中,即使找准了嫌疑对象,但收取的样本不符合鉴定条件,同样难以作出科学准确的鉴定结论。之所以出现这类情况,主要是因为侦查、检察、审判人员对笔迹样本应具备的条件认识不够,提取方法不当,以致一次送检样本就合格的很…     

签名笔迹量化检验研究用实验样本的设计与收集

本文在全面说明签名笔迹特点的基础上，阐述了签名笔迹特征层次结构模型的核心内容，重点探讨开展签名笔迹量化检验研究用实验样本的方案设计，收集方法与范围。同时，提出实验样本的设计与搜集应本着“贴近实战，服务办案”的原则，并具体设计了签名笔迹量化检验研究用实验样本的设计方案与具体内容，提出广泛收集具有代表性实验样本的具体要求。另外，提出了研究用实验样本筛选方法和扫描输入计算机具体要求。科学合理的设计与收集签名笔迹量化检验研究用实验样本，才能确保签名笔迹量化检验研究具体分析与统计结果的科学性和实用性。     

对笔迹书写相对时间的鉴定

对笔迹书写相对时间的鉴定曲新生笔迹书写时间的检验鉴定，根据检验对象和送检要求的不同，可分为两种类型：①笔迹书写绝对时间的检验鉴定。指应用科学的检验技术手段，确定某一检材上笔迹的具体书写时间；②笔迹书写相对时间的检验鉴定。指应用科学的检验技术手段，确定...     

浅谈文检鉴定工作中关于样本收集的一点体会

文检鉴定工作是通过检材的鉴定内容与样本之间的特征进行比对开展的,鉴定人员对案件材料予以种属鉴别和同一认定时,需将样本作为已知标准同检材进行比对。检材是特定唯一的,是不可改变的,而样本可以根据鉴定需要有针对性地选取与收集。因此提取的样本质量的高低,直接影响到鉴定工作和鉴定意见的准确性。本文介绍提取不同类型笔迹、印章印文样本的方法及注意事项,和大家一起探讨。     

试论正常笔迹的鉴定标准

正常笔迹鉴定标准是指：为规范正常笔迹鉴定活动，保障鉴定结论科学、可靠，以正常笔迹所反映的书写习惯为对象，针对鉴定活动中所涉及的检材、样本、字迹是否具备检验条件，笔迹特征的认定、分析、评断方法，鉴定结论的作出等技术问题所作出的统一规定。     

论笔迹鉴定中的量化检验

笔迹鉴定意见作为诉讼活动中不可或缺的证据类别之一,因其对鉴定人经验和专业知识的倚重,证据科学可靠性易受质疑。量化检验范式引入笔迹鉴定具不可估量的价值,本文试图撷取、梳理国内外理论实践对量化检验在笔迹鉴定中的成果,分析当下量化检验在笔迹鉴定运用中艰难性,从而探讨将定量检验和传统的定性检验有机融合的具体模式,以期为探索笔迹鉴定意见争议的庭审质证机制、笔迹鉴定争议解决模式与路径提供有益之借鉴,从而减少争议和重新鉴定的可能性,提升笔迹鉴定意见公信力。     

Microscopical discrimination of twins' head hair

Twin populations are ideal for studying human variation; a study of twin's hair, therefore, provided a better understanding of the value of hair comparisons. Duplicate head hair samples from 17 pairs of twins and one set of identical triplets were compared in a verified blind study. In addition to the direct comparison of all twins, random samples of two or three hairs were compared with randomly selected groups of known samples in a second blind study, to better simulate an ordinary forensic science case. Features commonly used by forensic hair examiners were adequate to distinguish hair samples from each twin from all other samples, illustrating the power of microscopical comparison when numerous questioned hairs are available in evidence. When two or three hairs were compared with randomly selected known samples, several were indistinguishable from hair samples other than the true source, proving once again that a human hair can never be associated with one person to the exclusion of all others.     

样本条件较差案件的笔迹检验和体会

文件检验案件,多数需要事先收集供比较鉴别的样本材料,可比的样本是鉴定人解决问题的已知标准。由于检察机关自侦案件在初查阶段具有隐蔽性的特点,大多数送检人提取的样本条件较差已成为鉴定人不得不正视的一个问题。本文结合工作实际,谈一谈检验此类案件的粗浅体会。     

Comparison of GSR Composition Occurring at Different Locations Around the Firing Position

Abstract: Variations in gunshot residue (GSR) compositions are used in the reconstruction of shooting incidents. In this study, GSR samples taken from seven different locations around and in the firearm were collected and analyzed using scanning electron microscopy/energy dispersive X‐ray analysis. Four different types of ammunition were applied. Very low correlations were found when different ammunition were used. This clearly shows that it is possible to differentiate between ammunition types. When the same ammunition was used, high correlations were found between samples taken from external positions (such as hands of shooter, bullet‐entrance holes) but poor correlation was found between internal samples (such as firearm barrel, cartridge case) and external samples. A high degree of association was found between samples that simulated victim and shooter. These findings clearly demonstrate that GSR comparison studies are meaningful but care needs to be taken when choosing suitable exhibits. External samples (such as hands of shooter, bullet‐entrance holes) are more suitable candidates than internal samples (barrel of the firearm, cartridge case).     

共聚焦显微镜检验工具痕迹的可行性研究

目的验证共聚焦显微镜能否用于工具痕迹检验;方法对实验样本分别用共聚焦显微镜和比对显微镜检测后进行效果比较;结果用共聚焦显微镜检验工具痕迹比用同倍的比较显微镜能发现更多细节特征;结论共聚焦显微镜可以用于工具痕迹检验。     

Driving under the influence of alcohol and/or drugs in the Netherlands 1995–1998 in view of the German and Belgian legislation

This study presents the test results of blood and urine samples of impaired drivers in the Netherlands between January 1995 and December 1998. In this period, the blood alcohol concentrations of 11,458 samples have been determined and 1665 blood or urine samples have been analysed for drugs. The median alcohol concentration was between 1.7 and 1.8 mg/ml blood. In 80% of the 1665 analysed samples drugs were detected. At least 42% (702/1665) of the impaired drivers were poly-drug users, with cocaine present in the most frequent combinations. In the Netherlands, the procedure to prove driving under the influence is complex. This procedure can be made more efficient and more effective by embedding the analytical test results, needed to prosecute an impaired driver, in the law. In Belgium and Germany, such laws already are in force. If we would apply the qualifications of the new Belgian law on our analytical data, 67% of the impaired drivers included in this comparison could have been prosecuted without discussion in court.     

A comparison study of hair examination methodologies

A study was conducted to investigate the accuracy between two methods of hair analysis: PCR-STR DNA analysis and microscopic comparison analysis. Standard sets of pubic hairs were collected from volunteers, and unknown sets were generated from these samples. Three out of five (60%) of the hairs analyzed produced full DNA profiles that were correctly matched to the standard sets. DNA analysis was inconclusive (partial or no DNA profile) for two out of five (40%) of the samples. In contrast, the microscopic comparison analysis correctly matched four out of five (80%) of the samples to the standard sets but mis-identified one out of five (20%) of the samples. These results reinforce the practice of preliminary microscopic hair examination in narrowing down a set of hairs for DNA analysis. Microscopic comparison analysis is sufficiently reliable to remain a rapid and inexpensive method for forensic hair analysis.     

Driving under the influence of alcohol and/or drugs in the Netherlands 1995-1998 in view of the German and Belgian legislation

This study presents the test results of blood and urine samples of impaired drivers in the Netherlands between January 1995 and December 1998. In this period, the blood alcohol concentrations of 11,458 samples have been determined and 1665 blood or urine samples have been analysed for drugs. The median alcohol concentration was between 1.7 and 1.8 mg/ml blood. In 80% of the 1665 analysed samples drugs were detected. At least 42% (702/1665) of the impaired drivers were poly-drug users, with cocaine present in the most frequent combinations. In the Netherlands, the procedure to prove driving under the influence is complex. This procedure can be made more efficient and more effective by embedding the analytical test results, needed to prosecute an impaired driver, in the law. In Belgium and Germany, such laws already are in force. If we would apply the qualifications of the new Belgian law on our analytical data, 67% of the impaired drivers included in this comparison could have been prosecuted without discussion in court.     

Effects of language mismatch in automatic forensic voice comparison using deep learning embeddings

In forensic voice comparison, deep learning has become widely popular recently. It is mainly used to learn speaker representations, called embeddings or embedding vectors. Speaker embeddings are often trained using corpora mostly containing widely spoken languages. Thus, language dependency is an important factor in automatic forensic voice comparison, especially when the target language is linguistically very different from that the model is trained on. In the case of a low-resource language, developing a corpus for forensic purposes containing enough speakers to train deep learning models is costly. This study aims to investigate whether a model pre-trained on multilingual (mostly English) corpus can be used on a target low-resource language (here, Hungarian), not represented by the model. Often multiple samples are not available from the offender (unknown speaker). Samples are therefore compared pairwise with and without speaker enrollment for suspect (known) speakers. Two corpora are used that were developed especially for forensic purposes and a third that is meant for traditional speaker verification. Speaker embedding vectors are extracted by the x-vector and ECAPA-TDNN techniques. Speaker verification was evaluated in the likelihood-ratio framework. A comparison is made between the language combinations (modeling, LR calibration, and evaluation). The results were evaluated by Cllr_min and EER metrics. It was found that the model pre-trained on a different language but on a corpus with a significant number of speakers can be used on samples with language mismatch. Sample duration and speaking style also seem to affect the performance.     

Distinguishing Characteristics of Robotic Writing

Advances in robotic handwriting technology create new challenges for forensic document examiners. In the past, devices such as the autopen were used to replicate signatures of government officials and corporate companies. In today's technology, companies such as Bond utilize robots to create written documents, which mimic natural patterns of handwriting. They generate customizable written samples by simulating pen movements and letter formations. Four forensic document examiners were given various reproduced questioned documents and utilized a modified ACE‐V (analysis, comparison, evaluation, verification) methodology to determine their genuineness. Examiners were able to make a distinction between the human writing samples and the skilled robotic equivalents. Several distinct features that are not seen in natural handwriting, such as even pen pressure and the superimposition of letterforms were observed in the robotic samples. Careful examination of identifying features of the Bond produced documents resulted in an opinion of nongenuineness.     

Analysis of glass fragments by laser ablation-inductively coupled plasma-mass spectrometry and principal component analysis

Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is used to differentiate glass samples with similar optical and physical properties based on trace elemental composition. Laser ablation increases the number of elements that can be used for differentiation by eliminating problems commonly associated with dissolution and contamination. In this study, standard residential window and tempered glass samples that could not be differentiated by refractive index or density were successfully differentiated by LA-ICP-MS. The primary analysis approach used is Principal Component Analysis (PCA) of the complete mass spectrum. PCA, a multivariate analysis technique, provides rapid analysis of samples without time-consuming pair-wise comparison of calibrated analyses or prior knowledge of the elements present in the samples. Probabilities for positive association of the individual samples are derived from PCA. Utilization of the Q-statistic with PCA allowed us to distinguish all samples within the set to a certainty greater than the 99% confidence interval.