现场指纹比对中细节特征的运用

在指纹自动识别系统中,指纹的数据文件由指纹原图文件和指纹特征点文件组成,而参与比对的只有特征点文件。特征点文件包含指纹的纹型、指位、中心点、中心半径、中心角度、细节特征、稀疏特征区域等项信息内容。在实际应用过程中,重点在反映指纹特点的基本信息上。     

尸体指纹的提取捺印

提取尸体指纹的方法通常采用油墨捺印和拉直器提取两种方法。在实际工作中,我们发现上述两种提取方法不易操做,且存在着一定的局限性,提取的指纹模糊不清且不完整,不利于比对检验和上网查询,特别是已僵硬变形、皱缩干瘪的尸体手指用上述方法很难提取。笔者通过实践,发现利用油墨粘取法,效果较好。具体方法是:先用酒精或清水清洗去尸体指纹上的污垢,待尸体指纹干燥后,用小油墨滚将油墨滚匀,直接均匀地滚在尸体十指指纹部位,然后用指纹胶带顺着指纹纹线方向粘取,即可得到纹线清晰不变形的油墨指印。如需当时检验,可将提取的指印粘在透明的物体…     

浅谈现场指纹比对中心点位置的确定

指纹中心点的位置确定对于指纹的自动识别具有关键的作用,中心点位置和中心轴线方向在多数有中心的现场指纹中不难确定,CAFIS指纹自动识别系统已为“中心半径”和“中心角度”设定了基本的误差范围,“中心半径”的基本误差范围为26,大约为三根纹线宽的距离。“中心角度”的基本误差范围为20度,这是系统设置的误差范围,但是,在实践中,我们经常将“中心角度”适当放大,特别是在现场指纹编辑后存入现场指纹库时,我们常将“中心角度”范围调大至30度。将弧形指纹和中心有伤疤造成中心位置不明确的指纹的“中心半径”范围调大到40度左右。在多数情     

尸体指纹的提取方法

在实际工作中，对于现场尸体十指指纹的提取，通常有两种提取方法：油墨捺印法、拉直器提取法。我们在工作实际中发现上述两种提取方法存在着一定的局限。特别是被浸泡，或被捆绑的尸体，手指极易僵硬变形、指肚干瘪、皱缩，提取条件差，如用上述方法很难提取。通过实践，笔者建立了一种银粉粘取法，效果较好。具体操作方法是：用酒精清洗尸体十指指纹，除去污垢；待清洗过的尸体十指指纹干燥后，用吸湿性好的银粉均匀刷在尸体十指指纹部位，刷粉不宜太薄、太厚要适度；银粉固定后用指纹胶带纸沿着指纹纹线方向粘取，粘取时，要使指纹胶与指…     

利用扫描仪将现场提取的指纹输入电脑

基层的现场勘查,大多还沿用以往的粉末刷显、胶带粘贴的方法。提取后的指纹,通常用135照相机加接圈来拍照后,再冲洗放大。由于基层刑事案件现场多,技术人员少,现场又受到光线条件和气候条件的影响,往往不能及时地拍照,使现场提取的指纹丢失。如何将现场提取的指纹不经任何处理,快速地输入到电脑内分类保存和比对呢?在没有专用软件的情况下,通过实践,在总结了多次失败的教训后,找到了一个利用普通扫描仪将现场提取的指纹不经任何处理就可以输入到电脑内的理想方法。1材料的选择将粉末显现出的指纹,用指纹专用胶带提取粘贴张白纸,否则扫描不出…     

现场指纹比对中细节特征和中心的运用

1 指纹细节特征 指纹自动识别系统是通过摄像机或扫描仪把指纹档案上的指纹图像转变成电讯号,经A/D变换后输入计算机,组成一幅二维灰度图像,进而实现它的特征抽取或结构分析。众所周知,一枚指纹的数据文件由指纹原图文件和特征点文件组成,而真正参与识别比对的只有特征点文件,特征点文件包含有指纹的纹型、指位、中心点、中心半径、中心角度、细节特征、稀疏特征区域等项信息内容,所以在比对时应将重点放在反映指纹特点的基本信息上。     

差异指纹比对关联要素分析

在指纹查询比对工作中，由于指纹自动识别系统系自动对十指指纹进行特征提取，检案人员应在把握系统特征比对算法基础上，根据已录入系统案件相关信息，如提取部位、提取方法、乳突线颜色等相对应的现场指纹进行研究分析，从而提高指纹比中率。笔者结合_T作实践，就如何利用指纹自动识别系统防止指纹漏检论述如下。     

现场灰尘指纹提取方法的探讨

灰尘指纹是一种在现场上经常需要处理的痕迹物证,最正规、最传统的方法就是用照相直接固定提取。但是,在现实现场勘查实践中,由于受现场条件、灰尘指纹本身条件或其所粘附客体条件的限制,要清晰完整地提取一枚灰尘指纹并不是一件容易的事。笔者在长期的现场勘查实践中发现,用胶带纸直接粘取指纹(再在暗室中用照相固定)的方法,不失为一种较为实际而理想的方法。1操作方法(1)在现场上的操作。勘查中如发现有灰尘指纹,先要观察灰尘的厚度、指纹是减层或加层和指纹的黏附客体,因为这3个方面都将决定提取指纹的质量;然后用胶带直接粘取,贴于一中…     

间接免疫酶组化法检测人指纹ABO血型

建立一套测定人指纹 ABO血型的方法体系。运用间接免疫酶技术和免疫印迹技术 ,对指纹胶纸提取的指纹、银粉显现提取的指纹、直接转移至硝酸纤维素膜 (NC膜 )上的指纹、银粉显现转移至 NC膜上的指纹、“5 0 2”胶熏显转移至 NC膜上的指纹等进行 ABO血型检测。上述 5种方法采集的 2 12枚指纹 ,绝大部分能正确地检出 ABO血型 ,检出率为 90 %～ 93.8% ;未能检出的样本为非分泌型人指纹。应用间接免疫酶技术及免疫印迹技术测定人指纹的 ABO血型的方法具有特异性强、准确可靠、检测方便等优点 ,在法庭科学中易推广应用 ,并能发挥重要的作用     

活体指纹图像质量自动评估的参数选择与实现

1前言随着计算机技术、信号信息处理和模式识别技术的乱,难以准确提取到中心点,而且为了提高比对精度,多数指纹算法对于模糊区在匹配时不参与比对。因此,模糊区域多或清晰区域少,都表明指纹质量差。2.1灰度均值和方差下式用于计算指纹灰度均值M和灰度方差Var,图像大小为N×N,G(i,j)是指纹图像第i行第j列的图像元素的灰度值。M=1N2∑N-1j=0∑N-1i=0G(i,j);VAR=1N2∑N-1j=0∑N-1i=0[G(i,j)-M]22.2均衡化均衡化是降低指纹脊线和谷线间的灰度偏差,调刑事技术2007年第6期整指纹灰度均值和方差接近给定的期望均值M0和期望方差Var0,均衡化…     

A Simple Computer‐assisted Quantification of Contrast in a Fingerprint

A simple method for quantification of contrast in a fingerprint is proposed. Contrast is defined as the average difference in intensity of pixels between valleys and ridges in a fingerprint. It is quantified from a scanner‐acquired image of the fingerprint using a histogram function of Adobe Photoshop. The method was validated with black inked prints and marks developed with aluminum powder. Moreover, we tested resistance of the method to rater‐dependent errors and dependence of the measurements on the resolution of an image and the model of the scanner. For both groups of fingerprints, the method gave coherent and easily interpretable quantitative values for contrast. There were no significant differences between measurements performed by different raters and by the same rater in a test–retest procedure. However, the method was found to be instrument dependent, as measurements were significantly affected by image resolution and the model of the scanner.     

指纹鉴定标准研究

通过对国内学术界关于指纹鉴定标准构建的几种思路的分析,经综合比较,选择符合点＂数量＂思路作进一步探讨。在简要分析国外指纹鉴定＂数量＂标准研究概况基础上,尝试提出新的＂指纹特征组合概率计算模型＂,并以概率计算方式论证了8个符合点作为鉴定标准的合理性,由此得出一些对指纹鉴定工作可能有现实意义的结论。     

A Comparison of Cleaning Regimes for the Effective Removal of Fingerprint Deposits from Brass

Abstract:  Effective removal of fingerprint deposits is crucial for experimentation related to the corrosion of metals by fingerprint deposits. Such removal is also necessary prior to deposition of test fingerprints. The effectiveness of four regimes in removing fingerprint deposits from brass is considered. Sustained wiping of the deposit with a tissue at applied pressures of up to c . 1430 Pa or rubbing while the brass was immersed in acetone both failed to remove completely all traces of fingerprint deposits. Heating the brass to 600°C was an effective remover; however, this also oxidized the surface of the metal except where inhibited by fingerprint deposits. The most effective regime, and the only one of the four that removed all traces of deposit without affecting the properties of the metal surface, was immersion in warm soapy water while rubbing with a tissue. We propose this as the preferred method for fingerprint removal.     

NFIQ 2.0用于指纹质量控制的可行性及方法

目的测试NFIQ 2.0标准计算指纹质量评分模块在活体采集和油墨捺印指纹质量控制上的可靠性,研究利用NFIQ 2.0指纹分值综合判断指纹质量的可行性和在实际工作中的使用方法。方法一是利用NFIQ 2.0模块接口程序结合VS2015 C#编程语言制作指纹质量评分软件。二是记录20张指纹图片放置在采集框上、下、左、右、中五个位置时NFIQ 2.0的分值,计算平均偏差、最大偏差和相对偏差。三是对在指纹数据库中随机选出的1334枚活体采集和油墨捺印指纹(8位灰度、500 dpi BMP格式指纹图片)进行评分,将得出的分值与通过人工检查该1334枚指纹在指纹系统中自动提取的特征所计算的特征准确率,形成线条图并制作拟合线,通过线条图和拟合线研究NFIQ 2.0分值与特征准确率之间存在的关系。结果从平均偏差、最大偏差和相对偏差分析,指纹图片放置位置对NFIQ 2.0分值的影响很小。利用线条图和拟合线进行统计时,NFIQ 2.0分值与特征准确率之间呈现出一定的对应关系,NFIQ 2.0分值高的指纹,系统自动提取的特征准确性相对较高,反之相对较低。并且,分值在41~100之间时,特征准确率稳定在80%以上。结论NFIQ 2.0标准计算指纹质量评分模块可以用于大批量活体采集和油墨捺印指纹的辅助质量检测,在实际工作中可将NFIQ 2.0模块嵌入活体采集软件和指纹系统档卡扫描中,设定合理的阈值,对提高指纹采集的质量检测效率和提升指纹采集质量将有较大帮助。     

浅谈对外来人口的指纹建档

指纹档案是情报资料的重要组成部分,已成为侦破各类犯罪案件的有效侦查手段。然而,在外来人口数量猛增,犯罪人数逐年增多,犯罪率居高不下的形势下,只建立违法犯罪人员的指纹档案,已适应不了新形势下的外来人口犯罪的控制和打击,而我国短期内还不能建立全民指纹档案,因此,有必要建立外来人口指纹档案。而且,现代科学技术也为外来人口指纹的采集、建库、识别等各个管理环节,提供了物质、技术方面的保障。     

Fingerprint error rate on close non‐matches

The accuracy of fingerprint identifications is critically important to the administration of criminal justice. Accuracy is challenging when two prints from different sources have many common features and few dissimilar features. Such print pairs, known as close non‐matches (CNMs), are increasingly likely to arise as ever‐growing databases are searched with greater frequency. In this study, 125 fingerprint agencies completed a mandatory proficiency test that included two pairs of CNMs. The false‐positive error rates on the two CNMs were 15.9% (17 out of 107, 95% C.I.: 9.5%, 24.2%) and 28.1% (27 out of 96, 95% C.I.: 19.4%, 38.2%), respectively. These CNM error rates are (a) inconsistent with the popular notion that fingerprint evidence is nearly infallible, and (b) larger than error rates reported in leading fingerprint studies. We conclude that, when the risk of CNMs is high, the probative value of a reported fingerprint identification may be severely diminished due to an elevated false‐positive error risk. We call for additional CNM research, including a replication and expansion of the present study using a representative selection of CNMs from database searches.     

探析高分辨率指纹特定条件下三级特征的稳定性

目的探索油墨捺印指纹显现三级特征稳定性的影响因素,排除主观条件的影响。方法在最适宜的条件下,通过油墨捺印采集不同压力下的指纹样本,清晰地显出指纹三级特征,用高分辨率扫描仪扫描试验样本,保存指纹样本,最后分析了指纹汗孔、细点线、纹线形态、皱纹等三级特征的反映性及稳定性,确定其鉴定价值。结果油墨捺印法对三级特征的反映性不够理想,汗孔、纹线形态特征、细点线特征及皱纹在不同压力下的稳定性较差。其中,各个三级特征在轻压下的反映性及稳定性较为接近实际,捺印的压力越大则三级特征变形越大,甚至完全变形成为另外一种特征。结论所以如果将此法应用于指纹比对时,仍需进一步的研究与改进。     

Visualization of Latent Fingerprint Corrosion of Brass

Abstract:  Visualization of latent fingerprint deposits on metals by enhancing the fingerprint-induced corrosion is now an established technique. However, the corrosion mechanism itself is less well understood. Here, we describe the apparatus constructed to measure the spatial variation (Δ V ) in applied potential ( V ) over the surface of brass disks corroded by latent fingerprint deposits. Measurement of Δ V for potential of 1400 V has enabled visualization of fingerprint ridges and characteristics in terms of this potential difference with Δ V typically of a few volts. This visualization is consistent with the formation of a Schottky barrier at the brass-corrosion product junction. Measurement of the work function of the corroded brass of up to 4.87 ± 0.03 eV supports previous results that suggested that the corrosion product is composed of p-type copper oxides. A model for the galvanic corrosion of brass by ionic salts present in fingerprint deposits is proposed that is consistent with these experimental results.     

Magnetic Fingerprint Powder from a Mineral Indigenous to Thailand

Abstract: A study was conducted to investigate whether natural magnetite (Fe₃O₄), which is an abundant mineral in Thailand, could be used as a magnetic powder in the detection of latent fingerprints. Because of the presence of impurities, powdered magnetite is only weakly attracted by a magnet and cannot be used as a magnetic fingerprint powder by itself. Mixing a small amount of magnetite powder with nickel powder greatly enhances the magnetic attraction. A mixture of magnetite powder and nickel powder in a mass ratio of approximately 1:100 was found to be suitable for use as a magnetic fingerprint powder. Fingerprints developed using the magnetite/nickel mixture on nonporous surfaces were found to exhibit good adherence and clarity. Using an automated fingerprint identification system, the number of minutiae detected in fingerprints developed by using the prepared powder on nonporous surfaces was found to be comparable to those detected in fingerprints developed by using a commercial black magnetic powder. The cost is lowered by more than 60%.     

乳突纹线局部形态特征在手印检验中的应用

在手印检验工作中,通过对乳突纹线局部形态特征的种类、特点及检验方法进行研究,并运用实际案例进行分析阐述,论证该类特征在手印检验中具有可操作性,能够提高残缺、少特征等疑难手印的利用率。乳突纹线局部形态特征的应用是对常规特征的重要补充,对手印检验工作具有实际意义。