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。     

Triazolam, handwriting, and amnestic states: two cases

This paper presents a discussion of handwriting in the amnestic state through two case reports associated with the phenomenon of anterograde amnesia following the use of therapeutic doses of triazolam, a rapid acting oral sleep inducing benzodiazepine. The fact that an individual executing a contract or signing a document may have no recollection of the writing event has significant implications for the questioned document examiner and other forensic science specialists. Since the issue of amnestic states and handwriting has received little apparent discussion in the forensic science literature, this paper outlines a number of issues of concern to the forensic science specialist.     

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.     

Forensic examination of effects of Parkinsonism on various handwriting characteristics

Parkinsonism is a neurodegenerative syndrome that causes impairment of motor skills in affected persons. Thus, adverse effects may be produced in the handwriting of persons suffering from Parkinsonism. Medication used for the treatment of Parkinsonism is known to subside certain motor defects for specific time intervals, showing slight differences or improvement in certain handwriting characteristics during those intervals on the same day as compared to the ones executed before medication. Certain handwriting characteristics affected due to Parkinsonism may be mistaken as forged features due to poor line quality, which can cause suspicion upon the authenticity of important legal documents. The present research work has been carried out to determine the effects of Parkinsonism and medication used for its treatment on handwriting. Handwriting/signature samples executed before and after the onset of Parkinsonism (both pre- and post-medication) have been randomly collected from 70 participants. These handwritings have been evaluated separately and compared inter-se for various handwriting characteristics with qualitative and statistical approach. The results have demonstrated significant changes in most of the characteristics in both affected writings of majority of participants as compared to their corresponding earlier writings. Thus, forensic document experts should be aware of the detrimental effects of Parkinsonism on handwriting in pre- and post-medication conditions of this ailment.     

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.