Individuality of handwriting

Motivated by several rulings in United States courts concerning expert testimony in general, and handwriting testimony in particular, we undertook a study to objectively validate the hypothesis that handwriting is individual. Handwriting samples of 1,500 individuals, representative of the U.S. population with respect to gender, age, ethnic groups, etc., were obtained. Analyzing differences in handwriting was done by using computer algorithms for extracting features from scanned images of handwriting. Attributes characteristic of the handwriting were obtained, e.g., line separation, slant, character shapes, etc. These attributes, which are a subset of attributes used by forensic document examiners (FDEs), were used to quantitatively establish individuality by using machine learning approaches. Using global attributes of handwriting and very few characters in the writing, the ability to determine the writer with a high degree of confidence was established. The work is a step towards providing scientific support for admitting handwriting evidence in court. The mathematical approach and the resulting software also have the promise of aiding the FDE.     

遗嘱笔迹鉴定研究

通过案例分析、比较研究而获得不同种类遗嘱笔迹特点，在此基础上分析鉴定的难点，并提出伪装书写遗嘱笔迹、受客观条件影响变化的遗嘱笔迹识别以及同一认定鉴定的方法要点。     

专业性练习摹仿签名笔迹鉴定的实验研究

目的本文通过实验对具有一定笔迹鉴定专门知识与不具备笔迹鉴定专门知识的人的练习摹仿签名笔迹进行实验分析研究。方法对两类人在练习的不同阶段形成的练习摹仿签名笔迹特征的一般状态表现,以及对其笔迹特征的形成、变化原因、鉴定价值分别进行了论述,并总结出其变化规律。结果为不同种类的练习摹仿签名笔迹的鉴定提供一定的识别和特征分析、评断的参考依据。     

笔迹特征的统计分析

目的探讨笔迹鉴定的客观标准。方法采用统计分析的方法对笔迹特征的性质、种类极其鉴定价值进行研究,对笔迹特征进行分类。结果探讨了笔迹特征鉴定价值的规律。结论对笔迹鉴定的标准化研究具有一定的意义。     

The effects of marijuana and alcohol usage on handwriting

In this study the handwriting of twelve individuals under the influence of marijuana, alcohol, and a combination of the two was compared with control samples. It was found that marijuana smoking in moderate amounts had less effect on the handwriting of the individuals than did alcohol. It was also found that when the two were combined the gross changes observed were probably due to the effect of the alcohol alone.     

Score-based likelihood ratios for handwriting evidence

Score-based approaches for computing forensic likelihood ratios are becoming more prevalent in the forensic literature. When two items of evidential value are entangled via a scorefunction, several nuances arise when attempting to model the score behavior under the competing source-level propositions. Specific assumptions must be made in order to appropriately model the numerator and denominator probability distributions. This process is fairly straightforward for the numerator of the score-based likelihood ratio, entailing the generation of a database of scores obtained by pairing items of evidence from the same source. However, this process presents ambiguities for the denominator database generation - in particular, how best to generate a database of scores between two items of different sources. Many alternatives have appeared in the literature, three of which we will consider in detail. They differ in their approach to generating denominator databases, by pairing (1) the item of known source with randomly selected items from a relevant database; (2) the item of unknown source with randomly generated items from a relevant database; or (3) two randomly generated items. When the two items differ in type, perhaps one having higher information content, these three alternatives can produce very different denominator databases. While each of these alternatives has appeared in the literature, the decision of how to generate the denominator database is often made without calling attention to the subjective nature of this process. In this paper, we compare each of the three methods (and the resulting score-based likelihood ratios), which can be thought of as three distinct interpretations of the denominator proposition. Our goal in performing these comparisons is to illustrate the effect that subtle modifications of these propositions can have on inferences drawn from the evidence evaluation procedure. The study was performed using a data set composed of cursive writing samples from over 400 writers. We found that, when provided with the same two items of evidence, the three methods often would lead to differing conclusions (with rates of disagreement ranging from 0.005 to 0.48). Rates of misleading evidence and Tippet plots are both used to characterize the range of behavior for the methods over varying sized questioned documents. The appendix shows that the three score-based likelihood ratios are theoretically very different not only from each other, but also from the likelihood ratio, and as a consequence each display drastically different behavior.     

生理因素和环境因素对双生子笔迹影响的研究

目的 研究双生子由于受共同生理因素影响,教育和环境影响对笔迹特征影响的差异.方法 收集了80对双生子的笔迹,采用统计分析的方法进行研究.结果 书写水平、字的大小、字形、字行间距、书写速度特征受生理因素的影响较大,环境因素对竖长、撇长、转折角度、页边、错别字、笔画变异、笔画形态、搭配比例、写法、笔顺特征的影响更大.结论 生理因素和环境因素对笔迹的影响并不是彼此完全独立的,二者往往通过复杂的方式交互作用影响笔迹,一级亲属笔迹鉴定中应注意的选择特殊性强的笔迹特征全面比较.     

光谱成像检验同种同色涂抹掩盖字迹研究

目的建立一种无损、灵敏、直观的同种同色涂抹掩盖字迹的显现方法。方法依据涂抹掩盖字迹油墨物质的同色异谱特征,利用可见光滤波型多光谱成像检验系统进行检验。结果黑色圆珠笔、蓝色圆珠笔、黑色签字笔和蓝色签字笔相互涂抹掩盖形成的同种同色涂抹掩盖样本,利用可见光滤波型多光谱成像检验系统进行检验,显效率分别为90.5%、69.1%、49.5%、78.6%,显现效果良好。结论多光谱成像技术可以显现同种同色涂抹掩盖字迹,且具有良好的显现效果。     

Forensic handwriting examiners' expertise for signature comparison

This paper reports on the performance of forensic document examiners (FDEs) in a signature comparison task that was designed to address the issue of expertise. The opinions of FDEs regarding 150 genuine and simulated questioned signatures were compared with a control group of non-examiners' opinions. On the question of expertise, results showed that FDEs were statistically better than the control group at accurately determining the genuineness or non-genuineness of questioned signatures. The FDE group made errors (by calling a genuine signature simulated or by calling a simulated signature genuine) in 3.4% of their opinions while 19.3% of the control group's opinions were erroneous. The FDE group gave significantly more inconclusive opinions than the control group. Analysis of FDEs' responses showed that more correct opinions were expressed regarding simulated signatures and more inconclusive opinions were made on genuine signatures. Further, when the complexity of a signature was taken into account, FDEs made more correct opinions on high complexity signatures than on signatures of lower complexity. There was a wide range of skill amongst FDEs and no significant relationship was found between the number of years FDEs had been practicing and their correct, inconclusive and error rates.     

Using automated comparisons to quantify handwriting individuality

The proposition that writing profiles are unique is considered a key premise underlying forensic handwriting comparisons. An empirical study cannot validate this proposition because of the impossibility of observing sample documents written by every individual. The goal of this paper is to illustrate what can be stated about the individuality of writing profiles using a database of handwriting samples and an automated comparison procedure. In this paper, we provide a strategy for bounding the probability of observing two writers with indistinguishable writing profiles (regardless of the comparison methodology used) with a random match probability that can be estimated statistically. We illustrate computation of this bound using a convenience sample of documents and an automated comparison procedure based on Pearson's chi-squared statistic applied to frequency distributions of letter shapes extracted from handwriting samples. We also show how this bound can be used when designing an empirical study of individuality.     

中文笔迹性别差异的研究

目的考察中文笔迹的性别差异。方法采用中文笔迹测验材料对236名大学生的书写样本进行了测量,并对笔迹特征进行了统计分析。结果男性的书写水平低于女性,男性书写速度比女性快,男性笔迹较潦草,轻重疾徐的节奏感较弱;男性书写时所留页边比女性小;男性笔迹的连笔比女性多,转折角度比女性大;男性笔迹的字行间距大于女性。     

On the discriminability of the handwriting of twins

As handwriting is influenced by physiology, training, and other behavioral factors, a study of the handwriting of twins can shed light on the individuality of handwriting. This paper describes the methodology and results of such a study where handwriting samples of twins were compared by an automatic handwriting verification system. The results complement that of a previous study where a diverse population was used. The present study involves samples of 206 pairs of twins, where each sample consisted of a page of handwriting. The verification task was to determine whether two half-page documents (where the original samples were divided into upper and lower halves) were written by the same individual. For twins there were 1236 verification cases -- including 824 tests where the textual content of writing was different, and 412 tests where it was the same. An additional set of 1648 test cases were obtained from handwriting samples of nontwins (general population). To make the handwriting comparison, the system computed macro features (overall pictorial attributes), micro features (characteristics of individual letters), and style features (characteristics of whole-word shapes and letter pairs). Four testing scenarios were evaluated: twins and nontwins writing the same text and writing different texts. Results of the verification tests show that the handwriting of twins is less discriminable than that of nontwins: an overall error rate of 12.91% for twins and 3.7% for nontwins. Error rates with identical twins were higher than with fraternal twins. Error rates in all cases can be arbitrarily reduced by rejecting (not making a decision on) borderline cases. A level of confidence in the results obtained is given by the fact that system error rates are comparable to that of humans (lower than that of lay persons and higher than that of questioned document examiners [QDEs]).     

防止茚三酮溶液扩散纸张字迹的研究

目的 解决茚三酮溶液在显现手印同时对纸张上字迹产生扩散作的问题;方法 分别采用茚三酮丙酮溶液,茚三酮氟利昂溶液,茚三酮石油谜溶液,茚三酮庚烷溶液作比较。结果 钢笔字迹用4种溶液均不易扩散;纸张上其它成份字迹用后两种方法显现手印时可有效保存纸张上文字原貌。     

Significance of sequence of strokes in Chinese handwriting examination

This paper reports a statistical study on the sequence of strokes of 61 commonly encountered Chinese radicals and characters written by 372 invited subjects. The distribution of different writing sequence of these Chinese radicals and characters was examined. Comparison of the sequence of strokes executed by the subjects with the standard rule of writing these Chinese radicals and characters revealed that around 60% of the subjects wrote in the correct sequence. Pair comparison of sequences of strokes in Chinese handwriting among the 372 subjects was also performed. The results demonstrated that no two individuals wrote all the 61 radicals and characters with the same sequence of strokes. The findings indicate that, despite some basic rules governing the writing sequence of Chinese characters, writers tend to develop their own habits. The findings also support the hypothesis that the handwriting of experienced writers is individual.     

On the "general acceptance" of handwriting identification principles

Informed by the admissibility requirements of the broad and narrow Frye tests as well as Daubert's general acceptance factor, the present study elicited the views of a homogeneous group of forensic document examiners and a heterogeneous group of handwriting scientists regarding the degree to which a set of principles relating to the nature of handwriting and its identification were generally accepted within the respondents' fields. Among forensic document examiners, the greatest agreement was found concerning the process of examination, and somewhat less agreement on other matters. Forensic document examiners and handwriting scientists appear not to agree on the acceptability of most of the propositions.     

基于银胶表面增强拉曼光谱检验蓝色书写字迹初探

目的用基于银胶的表面增强拉曼光谱技术检验蓝色签字笔字迹。方法取4种常见不同牌号的蓝色签字笔在其字迹上滴加微量银胶,用显微共焦拉曼光谱仪进行检验。结果不同品牌的蓝色签字笔字迹的表面增强拉曼光谱不同。结论基于银胶的表面增强拉曼光谱技术可用于纸张上蓝色签字笔字迹的检验。