Colorimetric measurements on small paint fragments using microspectrophotometry

The use of the Nanospec 10S microspectrophotometer (Nanometrics Inc.) as a colour-coding instrument for small paint fragments and individual layers within a layer structure is described.The CIE system of colour notation is discussed and numerical values for colours within the CIE system are derived from reflectance measurements made with the microspectrophotometer.     

The use of microspectrophotometry for the identification of pigments in small paint samples

The visible reflectance spectra of a number of common pigments are presented. These were measured between 380 nm and 900 nm in paint films using the Nanospec 10S Microspectrophotometer. This data can be used in combination with a computer program based upon simple Kubelka-Munk theory to identify the pigments in paint samples. The use of this approach in forensic science is illustrated by examples from recent cases.     

Analysis of thin-layer chromatograms of paint pigments and dyes by direct microspectrophotometry

The Nanospec 10S microspectrophotometer has been used to produce reflectance spectra over the 380–900 nm range from coloured thin-layer chromatography spots. The method has been applied to extracted paint pigments and to dyes from other materials examined in forensic science.     

Analysis and discrimination of architectural paint samples via a population study

This study involved the comparative analysis and discrimination of 964 architectural paint samples collected in the United States and Canada. The samples were evaluated to determine the extent to which randomly collected architectural finishes can be discriminated following standard operating protocols for paint analysis. The study also provides a basis for assessing the significance of a result in which a pair or group are undifferentiated. The techniques utilized were stereomicroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) with both backscatter electron imaging (BSI) and energy dispersive spectroscopy (EDS), and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). To assess the layer characteristics (e.g., number, color, sequence, thickness), stereomicroscopy was used with FTIR and/or SEM as needed. The use of visual and microscopic evaluations in concert with FTIR resulted in 42 undifferentiated pairs, a discrimination of 99.99%. Adding SEM and Py-GC/MS analysis resulted in further discrimination of 31 pairs, resulting in eleven undiscriminated pairs of samples. At the conclusion of the study, samples that remained undifferentiated proved to originate from the same source. Therefore, no random pairs were indistinguishable at the conclusion of all examinations.     

SEM检验漆膜厚度鉴别同种颜色的汽车油漆

目的研究扫描电子显微镜测量漆膜厚度的方法对颜色相近的汽车油漆的区分能力。方法应用扫描电子显微镜对不同汽车厂家生产的12块蓝色油漆进行总厚度及分层厚度测量,并对所得数据进行t检验分析。结果在所有两两比对的66组样品对中,在置信度为95％时,用总厚度及分层厚度进行区分,区分率达到100％。结论用扫描电子显微镜微观测量油漆样品总厚度及分层厚度的方法,可对颜色相近的汽车油漆进行有效区分。     

The classification and discrimination of glass fragments using non destructive energy dispersive X-ray microfluorescence

Frequency of analytical characteristics is best estimated on glass recovered at random. However, as such data were not available to us, we decided to use control windows for this estimation. In order to use such a database, one has to establish that the recovered fragment comes from a window. Therefore, elemental analysis was used both for classification and discrimination of glass fragments. Several articles have been published on the subject, but most methods alter the glass sample. The use of non destructive energy dispersive X-ray microfluorescence (microXRF) for the analysis of small glass fragments has been evaluated in this context. The refractive index (RI) has also been measured in order to evaluate the complementarity of techniques. Classification of fragments has been achieved using Fisher's linear discriminant analysis (LDA) and neural networks (NN). Discrimination was based on Hotelling's T2 test. Only pairs that were not differentiated by RI followed by the Welch test were studied. The results show that neural network and linear discriminant analysis using qualitative and semi-quantitative data establishes a classification of glass specimens with a high degree of reliability. For discrimination, 119 windows collected from crime scene were compared: using RI it was possible to distinguish 6892 pairs. Out of 129 remaining pairs, 112 were distinguished by microXRF.     

汽车罩光漆的ATR-FTIR法检验

目的通过对油漆样品罩光漆成膜物质的检验以区分不同汽车厂家的油漆样品。方法采用衰减全反射红外光谱法（Fourier Transform Infrared Spectroscopy Attenuated Total Reflection Spectroscopy,ATR-FTIR）研究15个汽车厂家提供的356份油漆样品的罩光漆成膜物质。结果在所有油漆样品中,丙烯酸漆出现的频率最高,氨基漆出现的频率最低;在所有厂家中,使用丙烯酸漆的厂家最多,使用氨基氨酯混合漆的厂家最少;在使用相同罩光漆的不同厂家的油漆样品中,通过比较红外谱图可以对样品进一步区分。结论 ATR-FTIR法能够在一定程度上区分不同汽车厂家的油漆样品,从而大大缩小侦查范围,对于涉车案件的快速侦破具有非常重要的作用。     

Color analysis of apparently achromatic automotive paints by visible microspectrophotometry

Chromatic secondary pigments are utilized in achromatic automotive paints to create unique paint systems. These pigments may not be observable in reflected light; however, utilizing visible microspectrophotometry (MSP) discriminating data may be gathered. This study analyzed 160 apparently achromatic automotive paints via this technique for spectral evidence of secondary pigmentation. These results were compared with visual observations made via polarizing light microscopy. Positive spectral results were attained in approximately 25% of the black and gray/silver topcoat sample sets, whereas the white topcoat and gray undercoat set yielded no probative spectral data. The black sample set did yield several samples that produced spectral evidence of pigmentation when no visual chromatic data was observed. The results of this study suggest that paint analysis schemes should incorporate visible MSP for apparently achromatic black and gray/silver paint samples.     

The use of microspectrophotometry to characterize microscopic amounts of blood

The use of a Nanospec 10 S microspectrophotometer to examine minute bloodstains is discussed. To satisfy criteria for chemical identity, absorption spectra were recorded before and after treatment of the blood with Takayama reagent. The technique is of value where only tiny particulate bloodstains are available for testing and in other specialized instances.     

Use of solid-phase double-antibody radioimmunoassay to identify species from small skeletal fragments

Protein radioimmunoassay (pRIA) offers the potential to identify species in small skeletal fragments submitted as forensic evidence. The technique consists of protein extraction followed by a solid-phase double-antibody radioimmunoassay using controls of antisera (raised in rabbits) and radioactive (iodine-125) antibody of rabbit gamma globulin (produced in donkeys). Species determination results from evaluation of radioactivity uptake. To demonstrate the potential of this technique, six known bone samples (three human and three nonhuman, including one from a deer [Odocoileus virginianus]) were submitted for blind analysis. pRIA correctly distinguished the human from the nonhuman samples. Using 200 mg or less of each sample, species of the deer specimen was identified correctly, given the choices of cow, deer, dog, goat, and pig.     

发射光谱分析微量油漆串并系列盗枪案

目的检验4个现场提取的残留油漆,为系列枪支被盗案件串并案提供依据。方法发射光谱分析油漆微量元素成份。结果4个现场提取的油漆微量元素成份一致,根据痕迹特征,属同一种工具所致。结论该方法经济快速、灵敏度高、用材量少,适用于微量元素分析。     

显微光谱成像技术在汽车油漆截面检验中的应用

目的对汽车多层油漆的横截面进行分层和比对研究。方法运用显微光谱成像技术对收集的12个省市623个汽车漆片样本进行分层,并对截面结构相同或相似的油漆样本进行了区分。结果 623个油漆样本均可以分层,分析出漆层为两层及以上的油漆样本数占总数的87.26%;截面结构相同或相似的油漆样本能够多层同时区分。结论该方法具有科学及实用价值,检验结果可靠,可见光谱成像技术完全可运用拓展到微量物证的检验中。     

常见油漆稀料的GC／MS的检验及分类研究

目的对常用油漆稀料的检验分析方法及分类进行研究,并建立SPME-GC／MS对纵火案件中油漆稀料快速、灵敏、准确的分析方法。方法采用SPME-GC／MS法对5种不同型号品牌的常见油漆稀料进行分析。结果确定了样品处理方法和仪器分析最佳条件。实验的5种油漆稀料样本根据组分特征和结构特征的不同可归纳为4类。结论该研究结果可为纵火案件中油漆稀料残留物提供一种新的检验方法和检验依据。     

The morphological characteristics of fragmentation injuries caused by low-energy random fragments]

Experimental investigations showed real possibility to perform stand laboratory modelling of blast trauma at any distance of fragmentation lesion. Process of interaction between injuring splinters and part of human body has both qualitative and quantitative expressions: different morphologic kinds of human body lesions are in accord with quite specific equivalent of energy parameters expressed via specific kinetic energy. Connections determined give the opportunity to solve special medical problems related to determination of distance between the victim and the blast centre in fragmentation injuring exposure according to character and volume of lesions.