Spatial and temporal influences on bacterial profiling of forensic soil samples

Bacterial content may be helpful in differentiating forensic soil samples; however, the effectiveness of bacterial profiling depends on several factors, including uniqueness among different habitat types, the level of heterogeneity within a habitat, and changes in bacterial communities over time. To examine these, soils from five diverse habitats were tested over a 1 year period using terminal restriction fragment length polymorphism (TRFLP) analysis. Soil samples were collected at central locations monthly, and 10 feet in cardinal directions quarterly. Similarity indices were found to be least related among habitats, while the greatest bacterial similarities existed among collection locations within a habitat. Temporally, however, bacterial content varied considerably, and there was substantial overlap in similarity indices among habitats during different parts of the year. Taken together, the results indicate that while bacterial DNA profiling may be useful for forensic soil analysis, certain variables, particularly time, must be considered.     

高效液相色谱法分离测定药酒中乌头碱的含量

目的建立药酒中乌头碱的高效液相色谱快速分析方法。方法以白酒添加乌头碱对照品对药酒样品的前处理方法、仪器测试条件、线性范围、精密度、回收率进行全面考察,建立定量分析方法。对药酒中所含乌头碱的浓度进行测定。结果该方法乌头碱在药酒中的线性范围是0.45～9.0μg·mL-1;日内、日间精密度分别小于3.1%和4.7%;回收率在(97.3±2.8)%以上。结论所建方法实用、便捷,可对药酒中乌头碱的含量进行快速检测。     

Investigating the Postmortem Molecular Biology of Cartilage and its Potential Forensic Applications

This study investigated the postmortem molecular changes that articular cartilage undergoes following burial. Fresh pig trotters were interred in 30‐cm‐deep graves at two distinct locations exhibiting dissimilar soil environments for up to 42 days. Extracts of the metacarpophalangeal (MCP) and metatarsophalangeal (MTP) joint cartilage from trotters disinterred weekly over 6 weeks were analyzed by Western blot against the monoclonal antibody 2‐B‐6 to assess aggrecan degradation. In both soil conditions, aggrecan degradation by‐products of decreasing molecular size and complexity were observed up to 21 days postmortem. Degradation products were undetected after this time and coincided with MCP/MTP joint exposure to the soil environment. These results show that cartilage proteoglycans undergo an ordered molecular breakdown, the analysis of which may have forensic applications. This model may prove useful for use as a human model and for forensic investigations concerning crimes against animals and the mortality of endangered species.     

Assessing three soil removal methods for environmental DNA analysis of mock forensic geology evidence

Soil is useful in criminal investigations as it is highly variable and readily transferred. Forensic geologists use several different techniques to removal soil from evidence prior to the analysis of inorganic components. There has been recent interest from the forensic science community to analyze environmental deoxyribonucleic acid (eDNA) associated with soil to augment existing forensic analyses. Notably however, limited research has been conducted to compare commonly used soil removal methods for downstream eDNA analysis. In this study, three soil removal methods were assessed: picking/scraping, sonication, and swabbing. Three mock evidence types (t-shirts, boot soles, and trowels) were sampled in triplicate with each removal method (n = 27). Soil samples underwent DNA isolation, quantification, and amplification of four genomic barcode regions: 16S for bacteria, ITS1 for fungi, ITS2 for plants, and COI for arthropods. Amplicons were prepared into libraries for DNA sequencing on an Illumina^® MiniSeq. DNA concentrations were highest in picked/scraped samples and were statistically significant compared with swabbed and sonicated samples. Amplicon sequence variants (ASVs) were identified, and removal methods had no impact on the recovery of the total number of target ASVs. Additionally, when assessing each sample in multidimensional space, picked/scraped samples tended to cluster separately from swabbed and sonicated samples. The soil core used a reference in this study also clustered with the picked/scraped samples, indicating that these samples may be more reflective of the communities collected from soil cores. Based on these data, we identified that picking/scraping is an acceptable soil removal method for eDNA analysis.     

mRNA在体液斑鉴定研究中内参基因的选择与应用

利用mRNA分析技术鉴定生物检材中各种体液斑迹的组织属性来源是近年来法医物证学的一个重要进展。终点逆转录PCR和实时荧光定量PCR技术是法医学实验室常用的mRNA检测技术,为保证实验结果的准确性,研究者通常选用组成性表达的管家基因作为内参,对不同样本提取RNA进行质控和标准化,以正确评估目标mRNA在各样本中的表达量。本文聚焦近年来使用mRNA分析技术进行体液斑迹组织属性来源鉴定的研究报道,对这些工作中内参基因的选择与应用效果进行综述。     

Factors affecting the forensic examination of automotive lubricating oils

Lubricating oil comparisons impact a variety of forensic investigations, including cases where oil was transferred from a suspect vehicle to the crime scene or victim. In this study, high-temperature gas chromatography/mass spectrometry was used to examine the influence of oil mixtures and oil changes over time on the comparison of known and questioned lubricating oils. Varying concentrations of oil mixtures were prepared and showed the potential for identifying individual components. Motor oils from 18 automobiles monitored over a 2-month period did not demonstrate significant changes in the chromatographic data. Chemometric analysis of motor oil mass spectral data provided little information regarding differentiation of, or changes in, the samples. Power steering fluid (PSF) from a naturally occurring leak collected from several locations was consistent with the PSF in the automobile's reservoir, and the PSF composition did not change over time.     

Soil forensics: How far can soil clay analysis distinguish between soil vestiges?

Soil traces are useful as forensic evidences because they frequently adhere to individuals and objects associated with crimes and can place or discard a suspect at/from a crime scene. Soil is a mixture of organic and inorganic components and among them soil clay contains signatures that make it reliable as forensic evidence. In this study, we hypothesized that soils can be forensically distinguished through the analysis of their clay fraction alone, and that samples of the same soil type can be consistently distinguished according to the distance they were collected from each other. To test these hypotheses 16 Oxisol samples were collected at distances of between 2 m and 1.000 m, and 16 Inceptisol samples were collected at distances of between 2 m and 300 m from each other. Clay fractions were extracted from soil samples and analyzed for hyperspectral color reflectance (HSI), X-ray diffraction crystallographic (XRD), and for contents of iron oxides, kaolinite and gibbsite. The dataset was submitted to multivariate analysis and results were from 65% to 100% effective to distinguish between samples from the two soil types. Both soil types could be consistently distinguished for forensic purposes according to the distance that samples were collected from each other: 1000 m for Oxisol and 10 m for Inceptisol. Clay color and XRD analysis were the most effective techniques to distinguish clay samples, and Inceptisol samples were more easily distinguished than Oxisol samples. Soil forensics seems a promising field for soil scientists as soil clay can be useful as forensic evidence by using routine analytical techniques from soil science.     

Developing and Testing a Soil Property Database for Forensic Applications in Southern California

The research sought to develop and test a forensic database of surface soil variability within previously mapped geologic and soil units in southern California. This type of database could be used to link suspects to crime scenes or determine source locations of soil sample evidence. Variability was evaluated using (i) color, (ii) magnetic susceptibility, and (iii) particle‐size distribution. Soil properties were analyzed for their ability to discriminate source areas using stepwise discriminant analysis. The percent correct predictions for geologic unit groups ranged from 30% to 100%. A blind study experiment matched four of the 18 samples to their unit of origin with the first choice by stepwise discriminant analysis, and eight were matched as second and third choices. The probability of selecting the appropriate unit of origin increased by 54% over random chance and eliminated as much as 99% of the field area as a potential search location.     

法庭科学中泥土物证XRF检验数据的分析研判

目的 对元素分析产生的大量数据进行统计,从而达到准确对样品进行区分和归类的目的.方法 利用X射线荧光光谱法对从北京郊区10个区县、辽宁沈阳、安徽泗县、四川泸州、山东威海和广西南宁提取的225个泥土样品进行元素定量分析.采用SPSS软件中欧氏距离计算泥土样品间的差异,利用主成分分析法进行样品归类.结果 确定了不同空间距离样品间差异的欧氏距离的阈值.主成分分析法可对225个泥土进行较为准确的分类.结论 欧氏距离值可为泥土样品的比对提供量化比对依据,利用主成分分析法可推断未知泥土样品的来源.     

Next‐Generation Sequencing of the Bacterial 16S rRNA Gene for Forensic Soil Comparison: A Feasibility Study

Soil has the potential to be valuable forensic evidence linking a person or item to a crime scene; however, there is no established soil individualization technique. In this study, the utility of soil bacterial profiling via next‐generation sequencing of the 16S rRNA gene was examined for associating soils with their place of origin. Soil samples were collected from ten diverse and nine similar habitats over time, and within three habitats at various horizontal and vertical distances. Bacterial profiles were analyzed using four methods: abundance charts and nonmetric multidimensional scaling provided simplification and visualization of the massive datasets, potentially aiding in expert testimony, while analysis of similarities and k‐nearest neighbor offered objective statistical comparisons. The vast majority of soil bacterial profiles (95.4%) were classified to their location of origin, highlighting the potential of bacterial profiling via next‐generation sequencing for the forensic analysis of soil samples.     

Assessing the potential of bacterial DNA profiling for forensic soil comparisons

A pilot study was undertaken to evaluate DNA profiling of the bacterial community in soil as an alternative to geological methods for forensic soil comparisons. Soil samples from three different ecosystems were compared, and the variation within and between ecologically different sites was determined by using terminal restriction fragment (TRF) analysis of 16S ribosomal DNA. Comparison of TRF profiles revealed that samples from within a specific ecosystem (e.g., a field) showed a significantly higher similarity to each other than to those from another ecosystem (e.g., a forest). In addition, some profile features were unique to specific ecosystems. These features may allow the determination of characteristic profiles that will facilitate identification of ecologically different sites, so that a given sample collected from a suspect could be identified as originating from, for example, a field, rather than a forest. The implications of these preliminary findings for forensic investigations are discussed.     

高效液相色谱法快速分离测定血浆中的乌头碱

目的建立血液中乌头碱的高效液相色谱快速分析方法。方法以空白人血浆添加乌头碱标准品对血液样品的前处理方法、仪器测试条件、线性范围、精密度、回收率进行全面考查,建立乌头碱定量分析方法。对血液中所含乌头碱的浓度进行测定。结果该方法在血液中的线性范围是0.1~5.0μg/m l;最低检测浓度为0.1μg/m l;日内、日间精密度分别小于3.7%和4.5%;回收率在(97.0±4.1)%以上。结论所建方法实用、便捷,可对血液中乌头碱的含量进行快速测定。     

SYBR GreenI实时荧光PCR技术在人类DNA定量中的应用

目的建立SYBR Green I实时荧光定量PCR技术在法医物证检验中的应用。方法应用SYBR Green I实时荧光定量PCR技术对各种生物检材进行定量分析,并在此基础上进一步分析STR。结果得到了实验的各种生物检材的准确定量。结论SYBRSYBR Green I实时荧光定量PCR技术是一种高效且廉价的检测基因拷贝数的方法,具有法医学应用价值。     

人血、尿中碘解磷定的高效液相色谱分析

目的建立人血、尿中碘解磷定的高效液相色谱分析方法,用于法医学鉴定和指导临床合理用药。方法以空白人血浆和尿液分别添加标准碘解磷定对样品的前处理方法、仪器测试条件、定性、定量分析方法进行考察和优化。对疑似有机磷中毒抢救或死亡者血、尿中的碘解磷定浓度进行测定。结果血、尿中碘解磷定浓度的线性范围是0.5~8.0μg/m l;定量检测的浓度限为0.5μg/m l;日内、日间精密度RSD≤5.3%(n=5);回收率:血≥(96.7±2.9)%;尿≥(93.7±3.8)%。结论所建分析方法快速、准确,适应于法医学鉴定和临床救治中碘解磷定血、尿浓度监测等相关研究。     

Applicability of DNA analysis on adhesive tape in forensic casework

Adhesive tape is commonly used in crimes and is often the subject of forensic evaluation. DNA analysis of adhesive tape can provide DNA profiles of suspects. The object of this study was to evaluate the applicability of DNA analysis on adhesive tape samples in forensic casework. We retrospectively reviewed all cases involving adhesive tape or similar items received by our institute for DNA analysis during the past 11 years. From 100 forensic cases reviewed, 150 adhesive tape samples were examined. A total of 98 DNA profiles were obtained from these samples. Sixty-two of the profiles provided feasible case-relevant information. In conclusion, DNA profiling of adhesive tape samples can be useful in a variety of forensic cases.     

The use of crossover immunoelectrophoresis to detect human blood protein in soil from an ambush scene in Kosovo

This study examines the survivability of human blood proteins in soils from a year and a half old ambush scene in Kosovo. A total of 72 soil samples were collected, a number of which were directly associated with bone fragments or bullet projectiles. The samples were examined using crossover immunoelectrophoresis (CIEP) to determine the presence of blood protein and species affiliation. Human blood proteins were identified in 44 of the 72 samples (61%) with the majority of the positive observations (29 of 44) found 0.0-4.5 cm below ground surface (65%). Chi-squared and two-sample difference of proportions tests confirmed significant differences between samples with and without associated physical evidence and the presence and depth of human blood proteins. While DNA has largely replaced immunological analysis in forensic analyses, our results suggest that in particular situations, CIEP may still be a valuable tool in criminology.     

SEM-EDS analysis and discrimination of forensic soil

Soils vary among different areas, and have some characteristics because of the natural effects and transfers made by human and other living beings in time. So that forensic examination of soil is not only concerned with the analysis of naturally occurring rocks, minerals, vegetation, and animal matter. It also includes the detection of such manufactured materials such as ions from synthetic fertilizers and from different environments (e.g., nitrate, phosphate, and sulfate) as environmental artifacts (e.g., lead or objects as glass, paint chips, asphalt, brick fragments, and cinders) whose presence may impart soil with characteristics that will make it unique to a particular location. Many screening and analytical methods have been applied for determining the characteristics which differentiate and discriminate the forensic soil samples but none of them easily standardized. Some of the methods that applied in forensic laboratories in forensic soil discrimination are the color comparison of the normal air-dried (dehumidified) and overheated soil samples, macroscopic observation, and low-power stereo-microscopic observation, determination of anionic composition by capillary electrophoresis (CE), and the elemental composition by scanning electron microscope (SEM)-energy dispersive X-ray spectrometer (EDS) and other high sensitivity techniques. The objective of this study was to show the effect of the application of 9 tonnes/cm2 pressure on the elemental compositions obtained by SEM-EDS technique and comparing the discrimination power of the pressed-homogenized and not homogenized forensic soil samples. For this purpose soil samples from 17 different locations of Istanbul were collected. Aliquots of the well mixed samples were dried in an oven at 110-120 degrees C and sieved by using 0.5 mm sieve and then the undersieve fraction(<0.5 mm) of these samples put on an adhesive tape placed on a stub. About 100-150 mg aliquots of dried, sieved samples were pressed under 9 tonnes/cm2 pressure by KBr disk preparation apparatus of an infrared spectrophotometer. Surfaces of the randomized particles and the pressed disks of the soil samples were scanned and the elemental compositions were determined with scanning electron microscope JEO-JSM-5600 equipped with an energy dispersive X-ray spectrometer OXFORD Link-ISIS-300. The samples from top of the sieves were examined with stereo-microscope equipped with JVC-TK-128DE color video camera and JVC-GV-PT2, digital video printer. Natural and artificial materials that have characteristic features were identified. Then for additional confirmation all soil samples were dried at 120 degrees C and over 780 degrees C and their colors compared. We concluded that pressing the whole sieved soil samples under 9 tonnes/cm2 pressure results in smashing over the harder particles into the softer matrix and results in homogenization of the soil sample. The elemental compositions of these samples obtained by SEM-EDS with 10-fold less standard deviation (S.D.) values and so that with more reproducibility and discrimination power.     

血液和尿液中草甘膦的净化富集及检测

目的建立血液、尿液中草甘膦的净化富集及定性定量方法。方法取适量血、尿样品,用80%甲醇水溶液稀释,经Agilent Accu Bond NH2（弱阴离子交换柱）净化富集,用3m L 5%氨水溶液洗脱后进行ESI/LC/MRM对草甘膦的定性及阴离子色谱法（IC）的定量检验分析。结果血液、尿液中草甘膦的IC法检验回收率均大于90%,方法的线性范围均在1-100μg/m L,血检测限为0.1μg/m L,尿液为0.08μg/m L。血液、尿液中草甘膦的LC/MRM的方法检测限均在5ng/m L左右。结论建立的血、尿中草甘膦的前处理方法和LC/MRM定性分析及IC定量分析方法,可满足司法检验要求。     

Microscopical discrimination of human head hairs sharing a mitochondrial haplogroup

In forensic analyses, determining the level of consensus among examiners for hair comparison conclusions and ancestry identifications is important for assessing the scientific validity of microscopical hair examinations. Here, we present data from an interlaboratory study on the accuracy of microscopical hair comparisons among a subset of experienced hair examiners currently analyzing hair in forensic laboratories across the United States. We examined how well microscopical analysis of hair can reliably be used to differentiate hair samples, many of which were macroscopically similar. Using cut hair samples, many sharing similar macroscopic and microscopic features, collected from individuals who share the same mitochondrial haplogroup as an indication of genetic relatedness, we tested multiple aspects that could impact hair comparisons. This research tested the extent to which morphological features related to ancestry and hair length influence conclusions. Microscopical hair examinations yielded accurate assessments of inclusion/exclusion relative to the reference samples among 85% of the pairwise comparisons. We found shorter hairs had reduced levels of accuracy and hairs from populations examiners were not familiar with may have impacted their ability to resolve features. The reliability of ancestry determinations is not yet clear, but we found indications that the existing categories are only somewhat related to current ethnic and genetic variation. Our results provide support for the continued utility of microscopical comparison of hairs within forensic laboratories and to advocate for a combined analytical approach using both microscopical analysis and mtDNA data on all forensic analyses of hair.     

Chemical fingerprinting of adhesive tapes by GCMS detection of petroleum hydrocarbon products

Pressure-sensitive adhesive tapes often represent key evidence of crimes such as assault, rape or homicide; thus, the development of analytical techniques able to contribute to a detailed characterization of these materials is of forensic importance. The gas chromatography-mass spectrometry (GCMS) analysis of the solvent extractable fractions of a suite of electrical and gaffer adhesive tapes spanning a range of colors and manufacturers identified a number of petroleum-derived hydrocarbons. Molecular and isotopic analyses of hydrocarbon constituents of complex materials have found wide analytical utility including the forensic investigation of oil spills and arson. Here, we investigate the utility of these techniques for characterizing the hydrocarbon composition of pressure-sensitive adhesive tapes for forensic correlation purposes. Subtle distinction of tape samples was evident in the GCMS distribution of several hydrocarbon groups including alkyl-naphthalenes, hopane and sterane biomarkers. Linear discriminant analysis of the abundances of these products provided high level differentiation of tape manufacturer. The distinction of different adhesive tape samples was further extended by measurement of their stable carbon isotopic values. The molecular and isotopic differences of the petroleum content of tapes are consistent with the use of different petroleum materials used in the manufacturing process and demonstrate the benefits of the combined use of complementary oil hydrocarbon characterization approaches. This study reveals the forensic potential of using established petroleum characterization methods for characterizing materials with a petroleum-derived hydrocarbon element.