Examination of the Sequence between Laser Printing and Rollerball Pen Writing Without an Intersecting Stroke

Examining the sequences of printing and writing is a significant method of determining the authenticity and validity of documents. Forensic document examiners have extensively studied crossing lines, which has produced useful information. However, the sequence for laser printing and rollerball pen writing without crossing strokes has not been studied. To solve this problem, volunteers were invited to write characters on A4 paper with different rollerball pens using two sequences. Four laser printers applied print to these sheets, and the materials were examined using an Optem A-Zoom2 video tomography microscope. Consequently, distinguishing features were noted between the materials produced in both sequences. These features might provide a scientific basis for accurately determining the sequence between laser printing and rollerball pen writing in the absence of intersecting strokes.     

数码单反相机成像特点及数字图像的后期处理

数码单反相机具有成像色彩饱和度低、焦点不实、反差低三大特点，针对其特点应改变设置，妥善进行图像处理。     

常用彩色激光打印机打印文件暗记特征的初步研究

目的收集当前我国常用不同品牌和型号的彩色激光打印机打印样本,研究打印文件上暗记特征的提取分析及其变化规律,探讨彩色激光打印文件暗记特征在鉴定实践中的应用及其在打印文件防伪措施中的价值。方法使用显微镜、文检仪及有关图像处理技术分别检验了彩色激光打印机的打印文件样本。结果彩色激光打印机打印文件上会出现暗记特征,且不同品牌的暗记特征出现规律、形态特征和点阵特征不同。结论暗记特征可作为初步鉴别彩色激光打印机品牌型号及打印时间的依据,具有防伪价值,但其在鉴定实践中还存在一定的局限性,有待进一步研究。     

Visualisation by confocal microscopy of traces on bullets and cartridge cases

The capabilities of confocal scanning laser microscopy for the visualisation of marks on bullets and cartridge cases were investigated. Confocal microscopy provides solutions to important limitations of conventional comparison microscopy with grazing light incidence, as generally used for the examination of these marks. It is expected that confocal microscopy, thanks to its broad applicability within the field of firearms investigation and its capability of non-destructively gathering quantitative three-dimensional information, will lead to a more complete and objective forensic examination of bullets and cartridge cases.     

Determination of the Chronological Order of a Laser Printing and Gel Pen Writing Without any Crossing Strokes

Laser printers and writing instruments are being exploited by the forgers to produce fabricated documents. They often produce such documents by appending genuine signature on a blank sheet and later printing on it. Often these fabricated documents do not contain intersection of strokes and may pose a difficulty to forensic document examiners in analyzing cases related to such documents. Keeping in mind the limited research work done on nonintersecting strokes, the present study has been conducted with an aim to determine the sequence of nonintersecting strokes of gel pens and laser printers. Three hundred samples of nonintersecting strokes of gel pen ink and laser printing were prepared. Of these 300, 150 had laser-printed text below the gel pen strokes and the remaining 150 were prepared with gel pen stokes below the laser-printed text. The samples have been analyzed using Nikon SMZ 800N stereomicroscope. Three micro-conformation features, that is, pattern of toner distribution, ink distribution, and fiber distribution have been observed in the samples. The results demonstrate the successful establishment of sequence of nonintersecting strokes in case of gel pen and laser-printed documents by the determination of micro-conformation features.     

Effects of histological staining on the analysis of human DNA from archived slides

Abstract: Archived slides of cell smears treated with histological stains for sperm detection are often the only source of DNA available when cold cases are reopened. There have been conflicting reports as to the negative effects of particular histological stains on DNA recovery and quality from human cells, making stain selection an important consideration for forensic laboratories. This study investigates the effect of several staining systems on DNA recovery from histological slide samples stored from 0 to 10 weeks. DNA profiles obtained after analysis of these samples with AmpFlSTR^® Identifiler? and increased cycle AmpFlSTR^® SGM Plus? short tandem repeat (STR) profiling systems and the effects that these stains have on DNA quantity and quality over time are described. Results indicate that Christmas Tree and Hematoxylin and Eosin stains do not have significantly different effects on DNA quality after 10‐week storage of slides. This research will assist scientists to select staining systems that have minimal deleterious effects on the DNA recovered.     

基于DNA预测人类可见外表特征的综述

本文介绍了基于DNA预测人类可见外表特征的法医学动机及筛选预测性DNA标记的科学挑战,讨论了目前认为很有应用前景的研究结果,比如现在科学水平只能达到通过高度关联的DNA标记准确预测性别、红色头发颜色、蓝色和棕色虹膜颜色。同时也讨论了现在看来不太有前景的应用,比如成年人的身高、人类面部特征等,为我国法医工作者今后进行相关研究提供一些参考。     

LAB图像处理模式区分黑色圆珠笔字迹的方法验证

目的考察验证LAB模式区分黑色圆珠笔字迹的方法,以及油墨浓淡对检验结果的影响。方法采用600dpi分辨率扫描样品并将图像保存成tiff格式,运用PhotoshopCS3图像处理软件中Lab模式进行处理。结果Lab模式无损区分黑色圆珠笔字迹的识别率达到61．67％,且油墨浓淡对实验结果影响不明显。结论此方法可用于黑色圆珠笔字迹的区分检验。     

Prediction of eye color from genetic data using Bayesian approach

Prediction of visible traits from genetic data in certain forensic cases may provide important information that can speed up the process of investigation. Research that has been conducted on the genetics of pigmentation has revealed polymorphisms that explain a significant proportion of the variation observed in human iris color. Here, on the basis of genetic data for the six most relevant eye color predictors, two alternative Bayesian network model variants were developed and evaluated for their accuracy in prediction of eye color. The first model assumed eye color to be categorized into blue, brown, green, and hazel, while the second variant assumed a simplified classification with two states: light and dark. It was found that particularly high accuracy was obtained for the second model, and this proved that reliable differentiation between light and dark irises is possible based on analysis of six single nucleotide polymorphisms and a Bayesian procedure of evidence interpretation.