一种石膏制模快速提取法

在农村发生的各类刑事案件中，多数现场为土质地面，现场遗留的犯罪痕迹中足迹出现机率最高。传统的石膏制模法固化速度慢，不能适应快速打击犯罪的需要。经比较实验，笔者发现向石膏液中加入促凝剂硫酸钠（Na２SO４）的方法，大大缩短石膏制模的固化时间，提高石膏模型的机械强度，且其他性能较传统提取法有所改善。现将实验报告如下：１原理由熟石膏溶入水生成生石膏凝固过程的化学式：C２＋＋SO２－＋２H２O→CaSO４·２H２O可知增加溶液中的SO２－离子的浓度可使平衡向右移动，加快CaSO４·２H２O晶体的析出速度，从而加速凝固…     

宁夏南部地带现场立体指纹石膏制模提取方法

近几年，随着农村耕畜价格的不断上涨，在宁夏南部农村，案犯采用攀爬越墙、挖洞人室等手段盗窃农机、耕畜的案件不断增加，在现场除留有工具、足迹等常见痕迹外，往往在现场出入口墙面及攀爬辅助物一一土坎上留有立体指纹。由于受散光及其它条件地限制，技术员很难用拍照等常规方法提取。     

犯罪现场平面足迹的提取

通过甄别后确定是犯罪嫌疑人所留的足迹,要根据其反映形式、形成条件以及承受客体的性质,采用不同的方法提取,现实当中最常用的为照相法.通过提取足迹后,可以进行进一步的足迹分析和鉴定,进而确定案件性质,划定和缩小侦查范围,提供侦查线索,确定犯罪,为诉讼提供有效证据.     

提取现场足迹的几种方法

足迹是犯罪现场最常见的痕迹物证之一,它不仅能反映出案犯在犯罪现场活动的轨迹,亦或多或少的隐含有犯罪分子的个体信息。现场勘查中,由于案犯的伪装、破坏、技术人员的勘查技能或现场客观条件等因素的制约,现场实际勘验中对足迹的发现、提取和利用往往不尽人意,利用传统的足迹发现和提取方法效果不太理想笔者在实践中发现有几种简单易行的方法,现列述如下:1灰尘减层足迹的提取对承痕体上灰尘层面厚、灰尘细腻且粘附性较强,足迹反映清晰,各种特征反映明显、稳定的,可以直接拍照或利用静电吸附器吸附后再拍照提取。对承痕体上灰尘层面薄,但承…     

水底足迹的提取方法

本文对水底足迹的提取方法进行了探讨,提出了提取水底足迹的CS法,新颖实用,可操作性强,效果良好.     

奶渍足迹的提取方法

随着人民群众生活水平的不断提高，牛奶作为一种常用饮品开始走进千家万户。在现场勘查中偶尔碰到犯罪嫌疑人在作案过程中将牛奶碰翻后，脚踏在牛奶上，在作案过程中形成奶渍足迹，而奶渍足迹多数为潜在足迹，笔者在实践中摸索出几种提取奶渍足迹的方法，介绍如下。     

血痕、泥水足迹与软质客体上加层灰尘足迹的提取

近年来,笔者在勘查现场时,常遇到光滑地面上已干涸的血足迹、泥水足迹,以及软质座垫上灰尘加层足迹,有时对其拍照后将其提取下来,时间短的血足迹和泥水足迹由于未完全干涸较容易提取下来,如果气温高、时间长,足迹会牢固地与地面结合在一起,很难用胶带粘下来,而软质客体上灰尘足迹采用常规方法提取的足迹又易变形,影响检验效果。笔者在实践中摸索到两种简便易行的提取方法,介绍如下:1血痕、泥水足迹的提取准备一条毛巾和一盆热水,将毛巾在水中浸温,稍拧一下,把温热毛巾打开平铺在足迹上,过几分钟后将毛巾移开,使干涸的血迹、泥土潮湿,稍干燥…     

光滑地面灰尘加减层足迹的提取

目前,室内地面装饰多以大理石、铀面砖及木地板为主,其特性为表面平整、光滑,对遗留在这类客体上的灰尘加减层足迹的提取,常规提取方法是打侧光直接照相或用静电吸附仪提取.但因客体表面颜色较浅或色彩不单一时,采用照相提取时效果较差;如用静电吸附仪提取,所用电压的高低,地面灰尘的多少,对所提取的足迹的效果影响较大,一些比较细小的特征在吸附后会变模糊或消失,而且静电吸附仪对木地板、塑料地板不起作用.笔者在工作中经多次实验,发现对这类足迹采用透明胶带粘取后拍照提取比较理想.     

成趟足迹提取方法导致误差的探讨

目的研究提取成趟足迹的低误差方法。方法比较相同条件下一次性拍照、分段连续拍照和扫描仪提取所产生的误差的大小。结果扫描仪提取法的误差最小。结论扫描仪提取足迹的方法易于掌握,适合基层技术员推广使用。     

对形象足迹和变形足迹的分析和检验的初步探讨

从足迹分析的角度,对犯罪现场上发现、提取的形象足迹和变形足迹在认定方面进行了初步探讨.     

Portable high‐resolution automated 3D imaging for footwear and tire impression capture

The forensic science community raised the need for improved evidence recognition, collection, and visualization analytical instrumentation for field and laboratory use. While the 3D optical techniques for imaging static objects have been extensively studied, there is still a major gap between current knowledge and collecting high‐quality footwear and tire impression evidence. Among optical means for 3D imaging, digital fringe projection (DFP) techniques reconstruct 3D shape from phase information, achieving camera‐pixel spatial resolution. This paper presents a high‐resolution 3D imaging technology using DFP techniques dedicated to footwear and tire impression capture. We developed fully automated software algorithms and a graphical user interface (GUI) that allow anyone without training to operate for high‐quality 3D data capture. We performed accuracy evaluations and comparisons comparing with the commercial high‐end 3D scanner and carried out qualitative tests for various impressions comparing with the current practices. Overall, our technology achieves similar levels of accuracy and resolution with a high‐end commercially available 3D scanner, while having the merits of being (1) more affordable; (2) much easier to operate; and (3) more robust. Compared with the current practice of casting, our technology demonstrates its superiority because it (1) is non‐destructive; (2) collects more evidence detail than casts, especially when an impression is fragile; (3) requires less time and money to collect each piece of evidence; and (4) results in a digital file that can easily be shared with other examiners.     

A comparison of three shoe sole impression lifting methods at high substrate temperatures

Footwear impressions are a common form of evidence found at crime scenes, and the accurate recovery and recording of such impressions is critical for shoe sole comparison and identification. The lifting of shoe sole impressions from hot surfaces (>30°C/86°F) and in hot environments has received little attention in the literature, particularly in relation to the recovery of class and randomly acquired characteristics (RACs) required for accurate comparisons. This study addressed this knowledge gap by comparing the performance of three common impression lifters (gelatin, adhesive, and vinyl static cling film) at recovering shoe sole impressions in dust from hot flooring substrates. Dry origin dust shoe sole impressions were made on ceramic tile, galvanized metal, and laminated wood flooring using a shoe that possessed two RACs and five class characteristics present on the sole. Substrates were left in direct full sun for five hours during a summer day prior to lifting. Performance was measured by the proportion of RACs and class characteristics visible in each lifted impression. Results demonstrated that the vinyl static cling film tested performed poorly across all substrates, particularly for metal (23.8% marks recovered), including notable shrinkage of the lifted impression. In contrast, adhesive (~96% marks recovered over all substrates), and to a lesser extent gelatin (~85%), lifts were highly successful on hot substrates. These data suggest that adhesive lifts can consistently and accurately recover shoe sole impressions from hot substrates. This study contributes critical information for crime scene examiners to improve and expand evidence recovery in hot environments.     

A comparative research of two lifting methods: electrostatic lifter and gelatin lifter

Two-dimensional dust shoeprints are often of very high resolution and contain unique features. Lifting these prints in the most effective method may contribute much to preserving these fine details. A research was conducted by experts from Israel and Switzerland to compare gelatin lifters and electrostatic lifters for lifting shoeprints. Several substrates were chosen, and on each material a set of dry dust shoeprints was made. A set of wet prints was made on paper as well. The shoeprints were approximately of the same quality, and the only variable was the nature of the material. On substrates indifferent to the method used, the preferable sequence was tested. Gelatin lifter was superior on most substrates and for wet prints. The superior sequence for using both methods is electrostatic lifting followed by gelatin lifter.     

Evaluation and comparison of the electrostatic dust print lifter and the electrostatic detection apparatus on the development of footwear impressions on paper

The Electrostatic Dust Print Lifter (EDPL) and the Electrostatic Detection Apparatus(2) (ESDA(2)) were compared to determine if both processes could be used to develop footwear impressions of the same or similar quality and in what order they should be used to develop the highest quality footwear impression. The sensitivity of each technique was also evaluated. The quality of the footwear impressions developed was determined by comparing 25 individual characteristics present on the known shoe to the footwear impressions developed using each technique. The footwear impressions were made by stepping on paper placed over several different surfaces, which included: linoleum, industrial Berber carpet, nylon carpet placed over a (3/8)-in. pad, ceramic tile, cardboard, 1-in. foam, 4-in. foam, cement, asphalt, grass, and mulch. Each of the papers placed on these surfaces was developed using the EDPL before the ESDA(2) and vice versa. The sensitivity test for the ESDA(2) was conducted by processing 10 sheets of stacked paper that were stepped on with the known shoe, beginning with the top sheet. The sensitivity test for the EDPL was conducted by processing 10 sheets of paper stepped on with the known shoe in succession. This study determined the footwear impressions developed using the EDPL were of better comparative value than impressions developed with the ESDA(2). On average, 72.4% of the individual characteristics from the known impression were identified on images developed when the EDPL was used first compared with an average of 38.9% when the ESDA(2) was used first. Therefore, if only one technique is used, the EDPL should be chosen. The sensitivity test determined the ESDA(2) develops high-quality footwear impressions on only the top sheet of paper. No footwear impressions were developed on any sheets under the top sheet of paper. The sensitivity test also determined the EDPL results increase in quality as the amount of dust residue decreases on the surface.     

足迹信息的计算机管理与查询

目的　根据国内足迹计算机管理系统的现状和需求 ,研制了适合我国刑侦工作特点的足迹管理与查询系统。方法　通过建立鞋厂鞋样、现场足迹和犯罪嫌疑人足迹数据库 ,利用足迹分析与比对软件进行管理和查询。结果　该软件完全能实现足迹管理计算机化 ,降低技术人员的劳动强度 ,提高足迹信息的使用率。结论　该软件使用方便快捷 ,适合推广使用     

The influence of footwear sole hardness on slip initiation in young adults

Slips occur when the friction demand of an individual exceeds the friction available from the shoe/floor interface. Shoe sole hardness is one of the factors thought to influence friction demand and available friction. The purpose of this study was to determine the influence of footwear sole hardness on the probability of slip initiation. Forty young adults were randomized into a hard or soft sole group. Slip events during the slippery floor trials were documented using a motion analysis system. The proportion of slip events in the hard sole group was greater than that in the soft sole group. The difference between utilized and available friction accurately predicted 90% of slip outcomes. Our data support the premise that individuals wearing shoes with harder soles are at greater risk for slipping. The results of this study suggest that shoe sole hardness should be considered when designing footwear aimed at decreasing slip risk.     

A Comparison of Enhancement Techniques for Footwear Impressions on Dark and Patterned Fabrics,

The use of chemical enhancement techniques on porous substrates, such as fabrics, poses several challenges predominantly due to the occurrence of background staining and diffusion as well as visualization difficulties. A range of readily available chemical and lighting techniques were utilized to enhance footwear impressions made in blood, soil, and urine on dark and patterned fabrics. Footwear impressions were all prepared at a set force using a specifically built footwear rig. In most cases, results demonstrated that fluorescent chemical techniques were required for visualization as nonfluorescent techniques provided little or no contrast with the background. Occasionally, this contrast was improved by oblique lighting. Successful results were obtained for the enhancement of footwear impressions in blood; however, the enhancement of footwear impressions in urine and soil on dark and patterned fabrics was much more limited. The results demonstrate that visualization and fluorescent enhancement on porous substrates such as fabrics is possible.     

Spectral enhancement of leucocrystal violet treated footwear impression evidence in blood

The results presented demonstrate the capacity for spectral enhancement to substantially improve the forensic examination of footwear impressions in blood treated with leucocrystal violet (LCV). The UV-Vis absorption spectra were generated of (i) an aqueous solution of leucocrystal violet, (ii) leucocrystal violet in 3% H(2)O(2), (iii) LCV working solution and (iv) whole blood added to LCV working solution. The resultant fluorescence emission spectra were subsequently generated (lambda(ex)=630nm, lambda(em)=661-900nm). The results indicate that the UV-Vis absorption spectra of an unbuffered solution of whole blood with LCV working solution produces a strong absorbance curve with a maxima at 630nm. Subsequent excitation at this wavelength and generation of the emission spectrum in the fluorescence mode indicates that a solution of whole blood added to LCV working solution is an extremely weak fluorophore. Therefore, to enable an adequate and timely enhancement of blood impression evidence treated with LCV utilising either visible fluorescence or infrared luminescence requires (i) selection of the most appropriate excitation wavelength (lambda(ex)) and emission wavelength (lambda(em)) with extremely narrow band pass filters, which in the absence of substrate matrix interference is excitation at 630nm producing the emission maxima at 665nm and (ii) a visual enhancement system such as a CCD colour IR video camera with image integration.     

Assessing the quality of footwear marks recovered from simulated graves

Footwear marks are one of the most frequently encountered evidence types recovered from a crime scene and can provide valuable scene intelligence regarding potential suspects. It has been acknowledged that impressions of footwear and tools can be recovered from graves, but previous studies have only focused on tool mark recovery. This has led to a lack of published information regarding footwear mark recovery from graves. It is therefore important to demonstrate whether the recovery of footwear marks is feasible and, if so, under what conditions this can be achieved. To address recovery, this study, placed 60 three dimensional (3D) impressions of footwear marks within 60 simulated graves. This was done to assess time (1, 2, 4 months) and at known depths (20, 30, 40 cm). The footwear marks within the graves were covered with clothing or left uncovered. The shoe’s design patterns were grouped and counted in a photographic comparison between the 3D footwear impressions, placed within the test-pits, and any recovered impressions. A grading system was adapted by the authors to score the quality of footwear impressions observed during recovery. The results demonstrate that the preservation and recovery of footwear impressions from graves is feasible. The simulated graves covered with clothing showed better preservation of footwear impressions, but there was no clear evidence that time or depth had an effect. The authors note that careful consideration and vigilant excavation skills are needed when excavating graves which may bear potential footwear marks, as their recovery will lead to an increased amount of intelligence that can link suspects to homicide scenes.     

A new method for casting three-dimensional shoeprints and tire marks with dental stone

Dental stone is used as the major material for recovering three-dimensional shoeprints and tire tracks from crime scenes. The procedure for using dental stone sparsely changed over the years. There are two common methods for mixing dental stone: (i) a premeasured amount of dental stone is put in a zip-lock bag to which water is added, and (ii) the water and dental stone are mixed in a bucket. We suggest a novel rapid and efficient method of mixing dental stone and water in a bottle. These methods were compared at equal conditions. The parameters measured were the number of air bubbles, the strength of the cast, the ease of use, and the sharpness and quality of the accidental characteristics present in the cast. The proposed bottle method has the advantages of both the bucket and the zip-lock methods hence it combines strength, sharpness, high quality, and ease of use.