潜血印迹显现方法研究进展

潜血印迹一般出现在恶性刑事案件当中,能够反映与案件有关的多方面信息,对于同一认定和分析判断案情具有十分重要的作用,这就使得其显现成为现场勘查的一项必不可少的工作。然而,这也正是公安实践工作当中的难点所在。经过多年的实验研究,目前国内外针对于潜血印迹的显现方法主要包括光学显现法和化学显现法。综述了这些常用显现方法的研究进展,并且讨论了每种显现方法在实践工作当中的优势和不足。     

The Identification of Spiromesifen,a Recently Introduced Pesticide,Using Approaches to Chemical Unknown Analysis

An unknown, viscous, opaque, white liquid with a strong, unpleasant odor was submitted with a request for identification. It was analyzed using infrared (IR) spectroscopy, gas chromatography–mass spectrometry, and X‐ray fluorescence spectroscopy. It was found to contain glycerin as well as another compound. IR and mass spectral data were readily obtained for this second component, but it was not easily identified as common instrument libraries had no matching spectra. After an extensive literature search, the unknown compound was identified as spiromesifen, a recently introduced pesticide. The IR spectrum and electron impact mass spectrum of spiromesifen are presented here as these are not available in the published literature. This case report also provides useful approaches for searching for and identifying an unknown compound when it is not found in a laboratory's spectral libraries.     

Recovery and detection of urea nitrate in traces

Urea nitrate (uronium nitrate, UN) is a powerful improvised explosive, frequently used by terrorists in the Israeli arena. It was also used in the first World Trade Center bombing in New York in February 1993. It is difficult to identify UN in postexplosion debris, because in the presence of water it readily decomposes to its original components, urea and nitric acid. A method for the recovery and detection of urea nitrate in traces is described. The residues are extracted with hot acetone, and the extract chromatographed on chromosorb G-HP. The eluent is analyzed by liquid chromatography mass spectrometry using atmospheric pressure chemical ionization (APCI). By applying this technique, we were able to identify urea nitrate in actual exhibits. It was found that UN can be also formed during the analytical procedure, by certain combinations of urea, nitrate ions, and a source of protons and, hence, the presence of the characteristic adduct ion does not necessarily indicate an "authentic" urea nitrate. Several solutions are suggested to overcome this ambiguity.     

The application of infrared chemical imaging to the detection and enhancement of latent fingerprints: method optimization and further findings

Fourier transform infrared (FTIR) chemical imaging allows the collection of fingerprint images from backgrounds that have traditionally posed problems for conventional fingerprint detection methods. In this work, the suitability of this technique for the imaging of fingerprints on a wider range of difficult surfaces (including polymer banknotes, various types of paper, and aluminum drink cans) has been tested. For each new surface, a systematic methodology was employed to optimize settings such as spectral resolution, number of scans, and pixel aggregation in order to reduce collection time and file-size without compromising spatial resolution and the quality of the final fingerprint image. The imaging of cyanoacrylate-fumed fingerprints on polymer banknotes has been improved, with shorter collection times for larger image areas. One-month-old fingerprints on polymer banknotes have been successfully fumed and imaged. It was also found that FTIR chemical imaging gives high quality images of cyanoacrylate-fumed fingerprints on aluminum drink cans, regardless of the printed background. Although visible and UV light sources do not yield fingerprint images of the same quality on difficult, nonporous backgrounds, in many cases they can be used to locate a fingerprint prior to higher quality imaging by the FTIR technique. Attempts to acquire FTIR images of fingerprints on paper-based porous surfaces that had been treated with established reagents such as ninhydrin were all unsuccessful due to the swamping effect of the cellulose constituents of the paper.     

Simulating transfer and persistence of a chemical marker powder for Lycopodium clavatum spores

In this research a chemical marker powder, based on Lycopodium clavatum spores, was studied to determine its transfer and persistence on a T-shirt. Such chemical marker powders are used to provide evidence that a person has handled a covertly marked object, such as a drug package. The powder was found to transfer readily between a marked item and the person handling it. The powder was found to persist on a T-shirt for up to 13 h; however, there was only a very small amount of powder remaining at this time. The rate of loss of the L. clavatum spores was found to follow a decay curve. The largest decrease in spores from the T-shirt was seen in the first 2 h after the marked item had been handled.     

Collection of Wet‐Origin Footwear Impressions on Various Surfaces Using an Electrostatic Dust Print Lifter

Electrostatic dust print lift method is known to be able to recover only dry‐origin footwear impression. However, the wet‐origin footwear impression could also be recovered using this method. As the amount of dust accumulated before deposition of the wet‐origin footwear impression increased, the intensity of the footwear impression lifted with this method became stronger. If the footwear impression is not affected by moisture after it is made, the 28‐h old wet‐origin footwear impression could be recovered using this method. The intensity of the lifted footwear impression did not decrease significantly even when the number of sequential steps increased as long as the shoe sole is wet. However, when the moisture on the shoe sole depleted, the intensity of the footwear impression decreased sharply. This method has the advantage of being able to enhance the footwear impression without being affected by the footwear impressions deposited in the past.     

应用于沥青路面的化学抑尘剂效果试验

对一种应用于沥青路面的化学抑尘剂,进行了现场抑制排放浓度和排放量的效果试验。抑尘剂应用于郊区沥青道路,对喷洒抑尘剂和未喷洒抑尘剂路段两侧颗粒物浓度进行测量,结果显示抑制PM10排放浓度效率为22%;抑尘剂应用于城区辅路,通过对抑尘剂喷洒前后路面粉土负荷的测量分析,根据AP-42排放因子公式模型计算颗粒物排放量,10%和3%两种浓度抑尘剂,28 d内抑制PM10排放量平均效率分别为49%和30%,35%浓度抑尘剂由于受工地干扰,效率为18%;抑尘剂应用于工地出口破损道路,对抑尘剂喷洒前后路边颗粒物浓度测量分析,结果显示2 d内平均抑制PM10排放浓度效率为82%,与洒水4 h内的效率接近但持续时间比洒水长。     

统计学方法在微量物证数据处理中的应用

统计学方法在微量物证理化检验工作中受到越来越多的重视,采用有效的统计学方法对检验数据进行分析,不仅能够深度挖掘复杂数据背后信息,还能不断提高数据的应用价值和证据本身的证据价值。本文对目前微量物证领域常用统计学方法进行归纳总结,简要介绍了常用统计方法的应用,对各类方法优缺点进行说明。最后,对法庭科学工作者都比较感兴趣的贝叶斯统计与似然比方法在理化检验数据统计分析中的应用进行了介绍。     

特殊文件相对形成时间的鉴定

伪造、变造、异常处理文书的书写时间鉴定在诉讼中的作用越来越重要。笔者在多年的文书鉴定工作中曾遇到多起特殊处理的文件,如人为老化文件、塑封文件,污染文件以及书写于传真纸、宣纸等特定材料上的文件,在对这些文件的检验过程中,笔者进行了部分研究,获得一些实际体会。     

刺激性毒剂希埃斯(CS)的检验

用化学显色法、红外光谱法(IR),以及色-质联用技术(GC/MS)分析具有强烈刺激性气味的毒剂希埃斯(CS),在缺少已知对照样的情况下,用以上方法,可做出准确的鉴定.