Investigating forensic document examiners’ skill relating to opinions on photocopied signatures

Many forensic document examiners are hesitant to express authorship opinions on photocopied handwriting as the photocopying process results in less feature information than original writing. This study aimed to test the accuracy of 15 examiners' opinions regarding whether photocopied questioned signatures were genuine or simulated. Each examiner received the same set of original signature exemplars, from one individual, and a set of eighty questioned photocopied signatures comprising of genuine and simulated signatures. The overall misleading (error) rate for the grouped examiners' opinions was 0.9% providing strong evidence that examiners can make accurate observations regarding the authorship of non-original handwriting.     

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.     

利用真签名伪造文书的识别与检验

通常情况下,绝大多数人认为,签名真伪决定了文书真伪。司法鉴定实际工作中,事实上签名真伪与文书真伪并不是等同关系。利用真签名伪造文书有许多方法。由于签名真是书写人的笔迹,因此在利用真签名伪造文书的实际鉴定中,鉴定人往往忽视系统检验,从而作出不符合客观实际的鉴定结论。在检验中,应充分根据利用真签名伪造文书不同方法出现的不同特点,综合运用案情分析法、细节特征比较法、图像软件分析法、仪器检验法、系统检验法进行检验。在检验过程中,还应注意受理案件时的材料是否为原件;案件情况中双方当事人矛盾的焦点;签名是真签名还是摹仿签名。     

Determination of vehicle speed from recorded video using the open-source software Kinovea

Video devices of different kind often record traffic accidents, including vehicle-pedestrian collisions and hit-and-run accidents. In these cases, the vehicle speed is valuable information because it can assist the investigators in an accident reconstruction. This paper examines the use of Kinovea, an open-source video annotation tool designed for sport analysis, to estimate vehicle speed in forensic videos. Kinovea does not require a complex methodology, and it can be used to make the calculation easily. A series of vehicle driving experiments using an appropriately calibrated speed radar system (so called Scout Speed) were carried out, and measurements were compared with the estimated speed. In controlled conditions, the comparison of Scout reference speed and calculated average vehicle speed by means of Kinovea found an average difference of 0.43 km/h, with a margin of error of ±0.64 km/h. In addition, further preliminary tests were carried out to check the reliability of the measurements under lower resolution conditions. Also, in these cases the calculations were in line with the ground truth. Therefore, in the tested conditions, Kinovea demonstrated to be an easy and reliable tool available for forensic video examiners. Further tests need to be conducted in order to address the applicability of the measurement technique with true CCTV/surveillance video recordings.     

利用车辆动力性原理计算事故车车速误差的探究

目的高速公路上追尾事故时有发生,事故责任判定常要求鉴定被追尾车的车速,尤其对超载货车的车速鉴定。方法本文利用车辆动力性与车速的关系对发生追尾事故的事故车车速计算问题进行了研究。结果应用此法明确了功率平衡方程中主要参数的不同取值对最终车速计算误差的不同影响程度。结论研究表明,滚动阻力系数与坡度两者的取值误差对车速计算结果影响明显,应予高度重视。     

机动车司法鉴定机构资质认定认可项目分类探讨

通过对国内机动车行业检测、检查、鉴定管理现状,归纳出社会对机动车司法鉴定主要需求,依据国家已经颁布的相关法律法规,分析机动车司法鉴定机构资质认定、认可的可行性,探索如何建立规范、合理、统一的机动车司法鉴定机构资质认定认可项目分类方法,并推荐了分类模式。     

汽车碰撞中乘员损伤成因分析与计算机仿真研究

目的运用计算机仿真技术模拟汽车碰撞过程,为法医学鉴定及交通事故处理提供参考依据。方法通过对汽车碰撞中乘员损伤成因分析及车辆痕迹检验,建立有效的人体、车辆仿真模型,利用动量冲量法与多刚体动力学结合仿真求解乘员运动模式,客观再现乘员交通伤特点。结果计算机仿真汽车碰撞过程中,人体模型上碰撞部位的分布符合法医学检验所得结果。结论计算机仿真求解乘员交通伤的方法在法医学鉴定和事故责任认定中具有参考价值。     

GC Analysis of Black Gel Pen Ink Stored under Different Conditions

In many criminal and civil cases in China, the most commonly questioned documents are those written with gel pen ink. An important task for forensic document examiners is to identify whether two or more ink entries in one or more documents were written with the same ink type. The identification of the age of gel ink entries made poses an important and difficult problem for forensic document examiners. In this paper, the volatile components of gel ink were determined and the gel ink was classified by gas chromatography with a flame ionization detector. Calibration curves were created to express the relationship between the content of volatile gel ink components and the age of gel ink entries stored under natural and UV‐induced aging conditions. The correspondence between the natural and UV‐induced aging conditions was also established. The experimental results showed that GC was useful in the analysis of black gel ink and applicable for determining the relative age of gel ink entries under certain conditions.     

车外人员撞击伤特点分析

目的以真实案例为基础,研究汽车碰撞事故中,不同机动车车型、不同交通方式等因素造成车外人员撞击伤的特征。方法选取上海地区发生的汽车与车外人员碰撞事故案例200例,通过对事故中的人、车等检验对比,分析车外人员撞击伤的特点。结果车外人员撞击伤主要出现在下肢,其次为胸部和头部;行人（含推车人）撞击伤出现频次与骑车人（含自行车或摩托车后座乘员）无明显差异;小轿车和小客车事故中撞击伤多见于下肢,大客车多见于胸部;车外人员被撞击后发生抛甩频率随车速的加大而增高,且通过车体痕迹检验,人体与车辆挡风玻璃发生（二次）撞击伤匹配程度最高。结论分析汽车与车外人员碰撞事故人体撞击伤特点,对于交通伤法医学鉴定及深化交通伤机制研究具有参考价值。     

监控视频中车辆平均速度测算方法比较

根据车辆速度计算公式,提出了两种基于监控视频测速的思路。一是视频图像与实地测量相结合,车辆运动距离通过与监控画面匹配后实地测量,运动时间通过视频帧率运算分别获得。二是利用车辆技术参数测量,在视频图像中,车身前后明显部位经过同一点,车辆运动距离和时间分别通过被测车型技术参数、视频帧率运算获得。并通过实验结果对两种方法进行评价。     

法证披露模型:应当向法证专家披露什么和法证专家应当披露什么?

法律上的披露问题主要集中在检控方向辩护方提供或者隐瞒了哪些证据。在本文中,我们将披露的概念扩展到更广泛的情境下,在这种情境下,披露失误可能导致误判。我们引入了一个概念模型,即“法证信息披露”,它涉及哪些信息应该披露给法证检验人员,以及法证检验人员应当披露哪些信息。本文全面概述了四类利益相关者的动态交互:法证服务、调查、法律和外部利益相关者。我们通过五个问题讨论了法证信息披露模式的有效实施,即如果要向法证检验人员或者由法证检验人员提供最好的信息,以提高法证决策质素,并尽量减少偏差,则什么时候进行披露?披露什么?如何披露?向谁披露?为什么披露?     

再看摹仿签名笔迹鉴定

由于签名笔迹字数少、可摹仿性强的特点,长期以来,摹仿签名笔迹鉴定始终是笔迹鉴定的难点。笔者从不同类型的摹仿方法出发,讨论不同方法下摹仿签名笔迹的特点,总结其特征规律。同时要重视笔迹鉴定过程中了解相关案情,为识别是否存在摹仿现象提供线索。在此基础之上,对比摹仿签名笔迹特征的变化规律,并从摹仿签名笔迹特征反映构成方面系统性地进行鉴定,鉴别是否存在摹仿签名的情况。通过撰写此文,以期对摹仿签名笔迹鉴定实务具有借鉴意义。     

Are expert penmen better than lay people at producing simulations of a model signature?

Although forensic signature examination is considered to be an identification science, it is a theoretical possibility that an individual may learn to forge another person's signature that is free from indications of simulation behaviours. This proposition was tested in a signature blind trial that was administered to 42 forensic handwriting examiners (FHEs). Participants expressed opinions on the authorship of 100 questioned signatures. The questioned signatures comprised a mixture of genuine, disguised and simulated signatures. Calligraphers formed part of the population of individuals who provided simulated signatures for the trial. A total of 3100 opinions were expressed of which 1254 were correct, 224 misleading and 1622 were inconclusive. Of the opinions expressed regarding the simulated signatures, the misleading score for the calligraphers' forgeries were approximately four times that of the lay persons' forgeries. These results provide strong evidence in support of the proposition that calligraphers are more skilled at simulating signatures than are lay people and can produce forgeries that some FHEs have difficulty detecting.     

Determination of average vehicle speed utilizing reverse projection

Reverse projection photogrammetry has long been used to estimate the height of an individual in forensic video examinations. A natural extrapolation would be to apply the same technique on a video to estimate the speed of an object by determining the distance traveled between two points over a set amount of time. To test this theory, five digital video recorders (DVRs) were connected to a single fixed camera to record a vehicle traveling down a track. The vehicle's speed was measured through Doppler radar by a trained operator and the speedometer of the vehicle was also recorded with a video camera. The recorded video was examined and the frames that best depict the beginning and end of the vehicles course were selected. Two reverse projection photogrammetric examinations were performed on the selected frames to establish the position of the vehicle. The distance between the two points was measured, and the time elapsed between the two points was examined. The outcome provided an accurate speed result with a standard degree of uncertainty. This study proves the feasibility of using video data and reverse projection photogrammetry to determine the speed of a vehicle with a limited set of variables. Further research is needed to determine how additional variables would impact the standard degree of uncertainty.     

A simple and effective image-statistics-based approach to detecting recaptured images from LCD screens

It is now extremely easy to recapture high-resolution and high-quality images from LCD (Liquid Crystal Display) screens. Recaptured image detection is an important digital forensic problem, as image recapture is often involved in the creation of a fake image in an attempt to increase its visual plausibility. State-of-the-art image recapture forensic methods make use of strong prior knowledge about the recapturing process and are based on either the combination of a group of ad-hoc features or a specific and somehow complicated dictionary learning procedure. By contrast, we propose a conceptually simple yet effective method for recaptured image detection which is built upon simple image statistics and a very loose assumption about the recapturing process. The adopted features are pixel-wise correlation coefficients in image differential domains. Experimental results on two large databases of high-resolution, high-quality recaptured images and comparisons with existing methods demonstrate the forensic accuracy and the computational efficiency of the proposed method.     

论法医学鉴定人出庭作证

本文探讨法庭作证的价值、方法。着重研究了法医学鉴定人的素质与鉴定结论的价值。最后息结指出只有高素质的法医学鉴定人才能承担新世纪的鉴定重任。使法庭作证永远走向成功。     

汽车罩光漆的ATR-FTIR法检验

目的通过对油漆样品罩光漆成膜物质的检验以区分不同汽车厂家的油漆样品。方法采用衰减全反射红外光谱法（Fourier Transform Infrared Spectroscopy Attenuated Total Reflection Spectroscopy,ATR-FTIR）研究15个汽车厂家提供的356份油漆样品的罩光漆成膜物质。结果在所有油漆样品中,丙烯酸漆出现的频率最高,氨基漆出现的频率最低;在所有厂家中,使用丙烯酸漆的厂家最多,使用氨基氨酯混合漆的厂家最少;在使用相同罩光漆的不同厂家的油漆样品中,通过比较红外谱图可以对样品进一步区分。结论 ATR-FTIR法能够在一定程度上区分不同汽车厂家的油漆样品,从而大大缩小侦查范围,对于涉车案件的快速侦破具有非常重要的作用。     

Validation of image stream hashing: A forensic method for content verification

How do forensic examiners know if they have altered an image stream when converting a digital image from one codec or file container to another for analysis? Forensic standards and best practices recommend avoiding alteration or degradation of multimedia data during transcoding. An image stream hashing method was recently introduced to the forensic science community to answer the question above. This paper offers an initial validation study of image stream hashing method that may answer the question above. The first half of the study's experiments tested the image stream hashing method to measure fitness for use in forensic science while identifying errors and limitations. The study's second phase analyzed the systematic errors detected in initial tests to discover error causation. Causation analysis identified four method limitations subsequently used to develop proposed standard controls of method operations. The final study phase repeated the initial experiments used in the first phase while implementing the proposed standard controls of method operations. Initial test results indicated the method had significant error rates, limiting the effectiveness of the method to only three of the five file types used in the study. The final testing phase revealed that implementing proposed standard controls of method operations reduced the potential systematic errors to a negligible level when using the image stream hashing method for content verification. The validation study concluded that examiners could use the image stream hashing method for forensic science only by implementing error mitigation techniques that utilize the proposed standard controls of method operations.     

系统鉴定方法在朱墨时序鉴定中的应用

朱墨时序鉴定是通过对印字交叉部位的检验,得出的印字先后顺序的判断。朱墨时序鉴定是文件鉴定的重要组成部分,它往往是判定文件物证真实性的重要依据之一。任何文件物证都是一个由多个要素组成的文件系统。通过介绍系统鉴定方法的原理、方法,以鉴定实践说明其在朱墨时序鉴定中的三种作用,同时也强调各种检验方法的综合运用。提倡在朱墨时序鉴定中,应运用系统鉴定方法,更加准确的把握印字交叉部位的表观特征,从而提高朱墨时序鉴定的准确性。