手印鉴定
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手印检测技术及其发展1.光学检验(1)光学检验的工作原理。
光学检验的工作原理是借助光源照射并调整入射光源的角度、位置及其方向发现并检验手印的。
多波段光源检测法是近年来新型的一种光学检测法,其能够发出从紫外到红外范围内不同波段光的新型光源,由于多波段光源具有光能量大、可选择光源多、较灵活方便的特点,而受到刑事技术工作人员的喜爱,并在日常的工作中大量使用。
(2)紫外光检验。
紫外光检验的工作原理是经过荧光试剂处理的手印遗留物质受紫外光的激发会发出特定的荧光,从而将指纹显现出来。
之后,使用专业的紫外照相相机对于显现后的指纹进行拍照固定。
紫外线照相主要作用是增强手印物质与留痕客体之间的反差,以此达到更好的手印提取效果。
在可见光范围内,大部分手印物质的反射能力与留痕客体的差别是不明显的,但是在紫外区域内,手印物质可以强烈吸收紫外线,而留痕客体的吸收率却很差,于是在紫外光激发下,显现的手印纹线与承痕客体之间产生较大的反差,从而最终显现出指纹。
利用手印物质与留痕客体在紫外区域照射下具有差异较大的反射吸收率,从而在感光材料上形成较大的反差,以此获得清晰稳定的手印图像就是物证检验摄影的原理。
依据紫外反射照相原理,短波紫外光源照射在留痕客体表面,留痕客体表面与手印中的汗液、油脂等物质在短波紫外线照射下反射效果产生差异,加大手印与背景之间的这种反差,实现潜在手印的光学显现,最后利用滤光镜、数码相机、翻拍架等摄影器材进行拍摄提取。
紫外照相法在实际的工作中,成功的解决了部分疑难手印的拍照提取问题,如陶瓷、镜面、搪瓷、部分塑料制品上的手印以及玻璃上双面重叠手印等,能够利用紫外线照相方法分离出清晰的指纹,并最终固定、保存。
(3)激光检验。
科学家B.E.Dalrymple,J.M.Duff在1976年鉴定年会上第一次提出可以利用氩离子激光器进行手印显现。
1978年,利用氩离子激光器进行手印显现成果被刊登在《法庭科学》上。
至此,对应用于手印显现技术的激光检验法的研究引起学界的广泛关注,相关研究方兴未艾。
英语六级写作技巧:写作常见错误解析一、语法错误(一)句子结构错误1.主从句叠置1) There are more and more students who like to use the computer. / More and more students like to use the computer.2) There are still many problems that should be noted and resolved. / Many problems still should be noted and resolved.2.简单句叠置I like chatting on line very much, so I go to the net bar almost every weekend. / I like chatting on line very much. I go to the net bar almost every weekend.3.从句叠置It is known to all that computers play an important role in many fields of our life. / As is known to all, computers play an important role in many fields of our life.4.句子成分缺失If we work hard, we will surely be successful. /Working hard, we will surely be successful.5.语序错误1) Why do college students spend more and more time on the computer?2) I often wonder where they have got their money.(二)动词形式错误1.时态错误Many people think that the Internet will be more useful in the future.2.语态形式错误1) I have been excited several days at the news that you willcome here.2) Most of the students are satisfied with the service in the dining hall.3.单复数形式错误1) Wise men seek opportunities rather than wait for them. /A wise man seeks opportunities rather than wait for them.2) Some people are afraid that computers may control men in the future.4.非谓语动词形式错误1) Let me say “hello” to you on behalf of everyone.2) Doing exercise in the morning is good for one’s health.3) Having studied in our school for 3 years, I find that the canteen service has changed a lot.(三)代词错误1) We can use computers in doing everything we like.2) A college student should be able to do his washing on his own.(四)冠词错误1) A/The horse is a useful animal.2) The exam will be held in December, 2004.(五)词性错误1) I wish you can consider my suggestions.2) If a person wantsto succeed, he must learn to endure sufferings and setbacks.二、用词错误1) Students must know how to operate a computer. / Students must know how to work on a computer.2) People can be exposed to many new things on the Internet. / People can learn many new things on the Internet.3) The purpose of this letter is to express some opinions onthe service in the dining hall. / The purpose of this letter is to make some complaints about the service in the dining hall.三、表达习惯错误1) What generated so large a change? / Why is there so largea change?2) Now 6000 yuan is enough for you to buy a P4 computer. / Now you can buy a P4 computer for 6000 yuan.3) In a room often live 6-8 students.4) I think there are three reasons for this great change.5) The prices of the food are too high. / The food is too expensive.6) The reason for this is that some people want to earn plenty of money without working hard. / This is because some people want to earn plenty of money without working hard.四、标点符号及大小写错误1) However, every coin has two sides. I think the surroundings in our canteen are the best among all universities.2) The man was racing down the street because he was late for the class.3) At last I want to let you know that I love our university very much.4) My favorite sports are swimming, jogging, mountaineering and playing table tennis.5) The best English film in my eyes is Forrest Gump.【英语六级写作技巧:写作常见错误解析】。
模糊变形手印检验的几点思考手印是犯罪调查和司法鉴定中常见的物证之一,其准确性和可靠性对案件的判决至关重要。
然而,手印在留存、提取、比对等过程中容易受到多种因素的影响,导致检验结果不够准确和可靠。
本文从模糊变形手印检验的角度出发,对几个关键问题进行思考和探讨。
一、模糊手印的特点及检验方法模糊手印是指因手指皮肤与物体表面接触不均匀或受到外力干扰而造成的手印模糊、变形或缺失的现象。
模糊手印的特点是模糊度高、细节少、信息量少。
因此,对模糊手印的检验需要采用特殊的方法和技术。
目前,常用的模糊手印检验方法包括:增强技术、显微镜技术、成像技术、三维重建技术等。
其中,三维重建技术是目前最先进、最可靠的模糊手印检验技术之一。
该技术通过对手印的三维几何形态进行还原和分析,可以大大提高手印的可读性和可比性。
二、手印变形的原因及影响手印变形是指手印与原始状态相比发生了形态上的变化,包括比例变化、形状变化、方向变化等。
手印变形的原因很多,主要包括:手指与物体表面接触不均匀、手指的压力不均匀、物体表面的材质和纹理等。
此外,手印的变形还可能受到环境因素的影响,如湿度、温度、光线等。
手印变形对手印的检验和比对带来了很大的挑战。
一方面,变形会导致手印的细节和特征发生变化,使得手印的可读性和可比性降低;另一方面,变形还可能导致手印与原始状态不一致,从而影响手印的比对结果。
三、手印比对的误差及改进方法手印比对是指将被发现的手印与犯罪嫌疑人或现场其他手印进行比对,以判断是否存在嫌疑人的证据。
然而,手印比对也存在一定的误差和局限性。
手印比对误差的主要原因包括:手印质量差、手印变形、手印的细节和特征不够明显、比对者的主观因素等。
为了减少手印比对误差,需要采取一些改进方法,如:1. 提高手印的质量:在手印提取和保存过程中,应注意保护手印的完整性和清晰度,避免手印受到外力的干扰和损坏。
2. 采用先进的手印检验技术:如三维重建技术、成像技术等,可以提高手印的可读性和可比性,减少手印比对误差。