现场足迹查询比对系统的可行性研究及应用

目的建立现场足迹查询比对系统,加强现场足迹的利用意识。方法以现场足迹文本查询、现场足迹图形特征查询和两者复合查询为比对系统的主要内容,并对现场足迹文本字段和足迹图形进行统一的科学界定。结果具有输入、浏览和异地查询功能。结论现场足迹查询比对系统能提高足迹的认定率,提高案件的并串质量和速度,达到破案目的。     

足迹查询系统串并案十战法

近年来,利用足迹破案的主要工作平台——足迹查询系统已在全国各地公安机关广泛应用,足迹查询系统大多采用省、市、县三级运行模式,具体地说：省、市级公安机关设立现场足迹库和犯罪嫌疑人捺印足迹库,并各自提供给下级单位进行查询比对;县级公安机关设立远程客户端,主要功能为录人现场足迹和犯罪嫌疑人捺印足迹,并能把这些足迹发送到省、市级足迹库中进行查询比对。     

“恒锐”足迹自动识别系统应用体验

足迹自动识别系统是一类高速度、高效率、低人力成本的刑事科学技术软件。随着城市外来人口的不断增多,跨区流窜作案数量呈逐年上升趋势,而推广使用足迹自动识别系统能对串并一系列跨区域流窜性案件、及时锁定犯罪嫌疑人、提高破案效率起到十分重要的作用。该文从案件与现场足迹录入、足迹图像处理与特征绘制、足迹查询与串并三方面探索该系统的实际应用,并对系统技术进展寄予厚望。     

足迹检验图像处理系统

足迹检验图像处理系统具有以下3个方面的功能:1.足迹图像处理;2.足迹图像检验鉴定;3.鞋样鞋底图文库管理。笔者在文中介绍本系统的分析年龄子系统,本文将介绍根据足迹图像分析身高、体态的子系统。     

足迹勘查重点及检验在凶杀案件中的作用

在现场勘查中,足迹是案件现场出现率最高的物证,但其运用被不断弱化,原因主要在于现场足迹提取合格率不高、样本足迹制作不规范、鉴定方法未被广大技术员所掌握、足迹档案管理方式老化等方面,很多技术人员往往忽视足迹在侦查破案中的作用,特别是在凶杀案的侦破中,对现场条件差、排查难度大的灰尘足迹更是不愿保护、显现和提取。而这种灰尘足迹很可能成为锁定犯罪嫌疑人,成功破案的关键所在。足迹检验鉴定如果能与压力分布系统、运动捕捉系统等科技有效结合,将使鉴定范围更宽广,结论更准确。     

立体足迹计算机自动识别系统的应用

足迹是犯罪分子在作案过程中遗留在承受客体上并能反映赤足或穿鞋袜的结构形态和人体行走动力的痕迹。在我国利用步法追踪和足迹检验认定人身起步于50年代,当时还是处于少数人掌握的经验阶段。上世纪80年代以后,在马玉林先生的步法追踪的基础上,科技工作者沿着形象特征和步法特征两条线索,使足迹检验的科学理论有了较大发展。在足迹认定人身方面,形成了诸多各有所长的检验方法。为了实现足迹检验现代化,笔者和有关部门共同研制了“立体足迹计算机自动检验系统(以下简称系统),介绍如下。1“系统”性能与功能1.1原理人体站立或行走条件下,脚掌…     

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。     

计算机技术在足迹方面的应用

利用计算机图像处理软件可以管理和处理足迹，以解决现场足迹长期保存、准确测量、快速排查等难题。首先建立计算机分类足迹库和足迹特征关键字，其次对输入的足迹进行高清晰度处理和特征关键字的准确测量，并将其存入分类足迹库，最后利用足迹特征关键字快速识别相似的足迹排除不同的足迹，并利用计算机软件强大的功能对识别的足迹进行进一步鉴定，这样就可大大提高足迹鉴定的速度和准确性。现场足迹，是罪犯进行犯罪活动时留下的比较多的痕迹，它是客观存在的，只要罪犯用脚站立、行走就会留下脚印。利用现场足迹不仅为侦察破案揭露、证实…     

指纹全国联网查询有利于打击各类流窜犯罪

随着全国各地公安系统指纹自动识别系统的建立,极大地提高了本地指纹查询的工作效率,比较充分地发挥了指纹档案在刑事侦查破案中的作用,有效地加快了刑侦科学技术发展的步伐。但是,当前各地公安部门的指纹管理和指纹鉴定都是区域性的,面对流窜犯罪日益增多的状况,区域性指纹管理的模式在一定程序上束缚了指纹自动识别系统的优越性。因此,应用各地指纹自动识别系统进行全国联网查询,就显得十分必要。     

青年人快速行走足底压力变化的研究

目的研究足底各区域压力分布的变化及其规律,为案件现场足迹分析提供理论基础与科学依据,促进足迹标准化与定量化检验。方法利用Footscan足底压力步态分析系统,采集15名青年人快速行走和常速行走时足底压力的数据,运用SPSS软件对两种步速下足底主要承重区域压力的分布特点作相关性分析和比较研究。结果足底各区域压力分布相关性不大,反映出压力有不同程度的改变。结论现场足迹分析时,应结合具体案情及犯罪嫌疑人的活动情况,准确把握足迹特征的变化以获得理想的分析结果。     

Application of non-contact scanning to forensic podiatry: A feasibility study

Foot impression evidence recovered from crime scenes can be available in the form of barefoot prints, sock-clad footprints, or as impressions within footwear. In some cases, suspects leave their footwear at the scene of the crime, and the insoles from the footwear can be important in linking a person to the footwear. The application of 3D data-collecting technology is becoming more and more popular within forensic science and has been used to recover footwear impression evidence. The present study is a feasibility study to discover if 3D data capturing devices can be applied to insoles; to capture the footprint impression for measurement using the Gunn method (a method used in forensic podiatry casework). Three different methods of data capture were conducted; Adobe Photoshop, MeshLab, and calipers used directly on the insole. Paired t-tests and Intraclass Correlation Coefficient (ICC) were conducted for all three data capture methods. Seven measurements used in this study were significantly different across all three methods. ICC scores were moderate to excellent for the Photoshop method, poor to good for the 3D method, and moderate to excellent for the Direct method.     

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.     

Statistical Discrimination of Footwear: A Method for the Comparison of Accidentals on Shoe Outsoles Inspired by Facial Recognition Techniques

Abstract:  In the field of forensic footwear examination, it is a widely held belief that patterns of accidental marks found on footwear and footwear impressions possess a high degree of "uniqueness." This belief, however, has not been thoroughly studied in a numerical way using controlled experiments. As a result, this form of valuable physical evidence has been the subject of admissibility challenges. In this study, we apply statistical techniques used in facial pattern recognition, to a minimal set of information gleaned from accidental patterns. That is, in order to maximize the amount of potential similarity between patterns, we only use the coordinate locations of accidental marks (on the top portion of a footwear impression) to characterize the entire pattern. This allows us to numerically gauge how similar two patterns are to one another in a worst-case scenario, i.e., in the absence of a tremendous amount of information normally available to the footwear examiner such as accidental mark size and shape. The patterns were recorded from the top portion of the shoe soles (i.e., not the heel) of five shoe pairs. All shoes were the same make and model and all were worn by the same person for a period of 30 days. We found that in 20–30 dimensional principal component (PC) space (99.5% variance retained), patterns from the same shoe, even at different points in time, tended to cluster closer to each other than patterns from different shoes. Correct shoe identification rates using maximum likelihood linear classification analysis and the hold-one-out procedure ranged from 81% to 100%. Although low in variance, three-dimensional PC plots were made and generally corroborated the findings in the much higher dimensional PC-space. This study is intended to be a starting point for future research to build statistical models on the formation and evolution of accidental patterns.     

The application of TreadMatch scans to aid the process of footwear mark comparison

Currently in the UK, if a person is arrested or charged with a recordable offence, they can have prints of their footwear taken whilst in custody. The tread pattern recorded in these prints can be searched for using the National Footwear Database to find out if the same footwear pattern has been recovered at previous crime scenes, generating forensic intelligence.TreadMatch is a digitised system for collecting footwear prints seized from detainees in custody for this purpose. Whilst its use for generating intelligence is accepted, validation experiments have not been conducted to understand its level of performance in assisting in forensic comparison purposes for identification, because in the absence of an incorporated scale, it is not known how well TreadMatch reproduces the pattern size of a tread, threatening the validity of the comparison. If it can be determined that the measurements of TreadMatch scans are consistent with the more commonly used aluminium powder test marks, this could save Police time and resources if the digital scans could be used for preliminary assessment prior to the footwear being physically submitted for evidential comparison. Therefore, this study set out to compare three different types of TreadMatch scans (‘dynamic’, ‘zoomed’ and ‘rolled’) for thirty different pieces of footwear, with test marks of the same footwear using the traditional method (fingerprint powder). Length and width measurements were obtained from each tread pattern using GNU Image Manipulation Program software. The resulting data were analysed to assess for agreement between TreadMatch scans and test marks using 95% Intraclass Correlation Coefficients (ICC) and 95% Bland-Altman plots of Limits of Agreement (LOA). Additionally, an intra-sample study using fifteen repeated measurements of the same piece of footwear for different TreadMatch scanning methods was carried out to support the larger validity study.95% ICC_3,1 resulted in coefficients ranging from 0.99 to 1.00 across all measurements. 95% LOA displayed close agreement. There was less agreement and more variation displayed between the test marks and the TreadMatch rolled scans for both length and width measurements. This variation for hand-rolled prints must be taken into consideration and a standard approach developed. The study suggests TreadMatch can be used for preliminary assessments in assisting forensic comparisons, particularly for dynamic and zoomed prints.     

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.     

Controlling the variable of pressure in the production of test footwear impressions

Footwear impression lifting and enhancement techniques may be affected by several variables introduced during the production of test footwear impressions, thus limiting the usefulness of enhancement technique comparisons and the results obtained. One such variable is the force applied when the impressed mark is being made. Producing consistent test impressions for research into footwear enhancement techniques would therefore be beneficial. This study was designed to control pressure in the production of test footwear impressions when mimicking a stamping action. Twenty-seven volunteers were asked to stamp on two different surfaces and the average stamping force was recorded. Information from the data obtained was used to design and build a mechanical device which could be calibrated to consistently deliver footwear impressions with the same force onto a receiving surface. Preliminary experiments using this device and different contaminants on the footwear sole have yielded consistent and repeatable impressions. Controlling the variable of pressure for the production of test impressions in this study demonstrated that the differences observed were visual (due to the amount of contaminant transferred and subsequent enhancement) and did not affect the replication of outer sole characteristics. This paper reports the development of the device and illustrates the quality of the impressions produced.     

Chemical enhancement of footwear impressions in blood on fabric — Part 2: Peroxidase reagents

This study investigates the optimisation of peroxidase based enhancement techniques for footwear impressions made in blood on various fabric surfaces. Four different haem reagents: leuco crystal violet (LCV), leuco malachite green (LMG), fluorescein and luminol were used to enhance the blood contaminated impressions.The enhancement techniques in this study were used successfully to enhance the impressions in blood on light coloured surfaces, however, only fluorescent and/or chemiluminescent techniques allowed visualisation on dark coloured fabrics, denim and leather. Luminol was the only technique to enhance footwear impressions made in blood on all the fabrics investigated in this study.     

Chemical enhancement of footwear impressions in urine on fabric

A range of chemical techniques were utilised for the enhancement of footwear impressions deposited on a variety of fabric types of different colours with urine as a contaminant. A semi-automated stamping device was used to deliver test impressions at a set force to minimise the variability between impressions; multiple impressions were produced and enhanced by each reagent to determine the repeatability of the enhancement. Urine samples from different donors were analysed using a spectrofluorophotometer revealing differences between individuals. Results indicated that the enhancement of footwear impressions in urine was possible using amino acid staining techniques whereas protein stains failed to achieve successful enhancement.     

Novices cannot fill the examiners’ shoes: Evidence of footwear examiners’ expertise in shoe comparisons

The value of a footwear examiner’s opinion centres on their ability to determine whether a particular shoe made an impression with greater accuracy than a novice. However, there has been limited research on the expertise of footwear examiners and the accuracy and reproducibility of their decisions. In the current study, we measured the accuracy and consensus of 31 footwear examiners versus a comparison group of 29 novices. Participants completed 20 ground truth known mock shoe comparisons. Results demonstrated that footwear examiners were more accurate than novices, regardless of comparison difficulty. Overall, on trials where probative decisions were given, examiners made false identifications and false exclusions on a total of 3% and 2% of trials, while novices made false identifications and false exclusions on a total of 19% and 17% of trials. Examiners also demonstrated better consensus in their opinions than novices, although both groups demonstrated low levels of agreement in their responses and variability in their interpretation of the conclusion scale. In summary, these findings support the proposition that footwear examiners show expert-level performance in matching known and unknown footwear impressions. These performance estimates may help the criminal justice system to appropriately value footwear examination evidence.     

Chemical enhancement of footwear impressions in blood on fabric — Part 3: Amino acid staining

Enhancement of footwear impressions, using ninhydrin or ninhydrin analogues is not considered common practice and such techniques are generally used to target amino acids present in fingermarks where the reaction gives rise to colour and possibly fluorescence. Ninhydrin and two of its analogues were used for the enhancement of footwear impressions in blood on various types, colours and porosities of fabric. Test footwear impressions on fabric were prepared using a specifically built rig to minimise the variability between each impression. Ninhydrin enhancement of footwear impressions in blood on light coloured fabric yielded good enhancement results, however the contrast was weak or non-existent on dark coloured fabrics. Other ninhydrin analogues which have the advantage of fluorescence failed to enhance the impressions in blood on all fabrics. The sequential treatment of impressions in blood on fabric with other blood enhancing reagents (e.g. protein stains and heme reagents) was also investigated.