Macroscopic assessment of environmental trace evidence dynamics in forensic settings

Environmental trace evidence offers useful circumstantial intelligence to link persons and scenes of forensic interest. An increasing empirical research base is dedicated towards understanding the transfer and persistence dynamics of environmental indicators including pollen, soils, and diatoms, within a diverse range of experimental frameworks. This paper presents two discrete studies exploring transfer and persistence of soils and sediments on footwear and diatomaceous earth adhered to clothing in forensically pertinent scenarios. Variables including sediment type, foot position, clothing type, and body positioning were also explored throughout. Both experiments incorporated a field-based methodology during the sampling effort. Photographs were collected of an initial transfer sample and of a retained assemblage following hours, days, and up to one-week of wear, facilitating macroscopic assessment of trace evidence dynamics. All images were processed using accessible, open-source software before spatial analysis of evidence distribution within and temporal assessment (% retention) upon each evidential surface. The results highlighted consistent loss of transferred sediment from footwear with significantly greater retention of loamy clay soil than dune sand which was absent beyond 24 h of wear. Loss was not influenced by wearer gait but was more rapid from those areas of the shoe sole in direct contact with the ground. Diatomaceous earth was retrieved from all three clothing types tested after one week – significant losses of material occurred before 48 h with a consistent assemblage identified beyond this. Denim was significantly more effective than acrylic and fleece for diatomaceous earth retention and significantly more material was lost from clothing worn on the lower body. These findings highlight the value of using visual environmental markers and a macroscopic analytical approach during the investigation of environmental trace dynamics. The methodology offers a novel, non-destructive assessment of soil and diatom transfer and persistence, complementing more extensive laboratory-based examinations to ensure the development of a well-rounded research base within the forensic sciences.     

Colonization of diatoms in and on porcine bone substrate and considerations of diatom ecology for forensic science

The presence of diatom algae in bone marrow has been used as forensic evidence of drowning for several decades; however, these studies are based on known or suspected recent drowning events. This study addresses the potential for diatoms to enter the bone marrow of skeletal remains, that is, de-fleshed long bones post-mortem. In laboratory and field experiments, bones were either inflicted with two access points by a cut and acid pitting or left intact. The bones were submerged in water for at least 1 week and up to 3 months. Samples of the bone surface and marrow were inspected for diatoms. The analysis considered the time required for diatoms to enter marrow and whether genus characteristics like size or mobility affect entry. The presence of an access point influenced diatom entry in that bones without an introduced access point had zero to one diatom present in the marrow, whereas a bone with an access point had >150 diatoms present in the marrow. The results of both laboratory and field phases suggest that diatoms will reliably colonize bone in as quickly as 1 week, establishing and maintaining communities for at least 3 months. However, the bone surface assemblages differ from the source community. Bone marrow displayed even more restrictive access to diatom colonization, resulting in communities dominated by small raphid diatoms. Based on these findings, we suggest some caveats on the use of diatoms as trace evidence in forensic science with recommendations for future avenues of research.     

辽宁省主要河流冰封期及开河后浮游硅藻变化规律

目的观察分析辽宁3条河流中浮游硅藻数量及种群构成在冰封期及开河后的变化规律,探讨其在法医学应用中的意义。方法于2012年1～4月中旬分别在辽河、浑河沈阳段及太子河本溪段布点取水,逐月观测硅藻数量及种群构成的变化规律,计算3条河段各月水样中硅藻数量平均值（个／10mL）以及主要硅藻属种及其构成比。结果3条河流冰封期及开河后硅藻种属数量和构成比均有明显变化。在冰封期（1～3月）硅藻种属数量趋于稳定,中心纲硅藻为优势种群,仅见少量羽纹纲硅藻,各月之间硅藻数量变化缺乏统计学差异;初春开河后（4月）硅藻种属数量显著增加,与冰封期差异明显（P〈0．01）,中心纲及羽纹纲硅藻混杂存在。结论辽宁主要河流在冰封期及开河后水中硅藻种群构成及数量变化大,春季水中浮尸的死因鉴定及落水点判断应合理分析现场水样与脏器中硅藻种群及数量差异。     

Clothing damage analysis and the phenomenon of the false sexual assault

This paper describes three recent false sexual assaults examined at the Victoria Forensic Science Centre laboratory where clothing damage analysis assisted in the resolution of the case. Suspected false reports of sexual assaults are often sensitive cases with little other forensic evidence. Any evidential value that can be obtained is thus valuable in order to minimize any ordeal to the complainant and any suspect and to conserve valuable resources. The findings illustrate the application of clothing damage analysis in a cross section of confirmed false sexual assault reports and the fact that the forensic examiner should be aware of the potential evidential value of this kind of analysis. Furthermore, the corroboration of a victim's scenario when the investigator has doubts may be no less valuable as it may minimize the adversarial ordeal that is often faced by a rape victim.     

An Improved Method for the Diatom Test Utilizing DNA Binding Ability of Silica

In order to devise a better forensic test for diatoms, the DNA binding ability of the diatom frustule constructing by silica, in the presence of chaotropic ions were utilized. It was proved that the diatoms were able to be captured via λDNA using silica‐coated magnetic beads (Mag beads), followed by isolation and purification from the Mag beads as a solid phase by substituting the chaotropic agent with ultrapure water. Five cases of drowning, three in freshwater and two in seawater, were applied to the present method and similar results as the usual diatom test were obtained. Specimens of lung and other organs were rendered clearly visible, with elimination of foreign impurities. The present method appears applicable for detection of diatoms indirectly using PCR amplification of bound DNA or directly staining of the DNA.     

Recovery of trace DNA and its application to DNA profiling of shoe insoles

In recent years, the analysis of trace amounts of DNA has become a necessary and useful forensic tool. DNA profiles can be obtained from items that have been worn or handled, due to the presence of transferred DNA derived from skin cells. Shoeprints collected from crime scenes that match a suspects shoe can link a shoe to the crime scene. A DNA profile from inside the shoe can link a wearer to a shoe thus increasing the evidential value of the forensic evidence. In this work, variation in the amount of DNA recovered from hands and feet of different individuals is investigated. Sites for sampling DNA from shoe insoles are compared and a protocol for the subsequent sampling and extraction is developed. Finally, a case study is described where DNA analysis of shoe insoles has provided forensic evidence.     

The relevance of the evolution of experimental studies for the interpretation and evaluation of some trace physical evidence

In order for trace evidence to have a high evidential value, experimental studies which mimic the forensic reality are of fundamental importance. Such primary level experimentation is crucial to establish a coherent body of theory concerning the generation, transfer and persistence of different forms of trace physical evidence. We contend that the forensic context, at whatever scale, will be specific to each individual forensic case and this context in which a crime takes place will influence the properties of trace evidence. It will, therefore, be necessary in many forensic cases to undertake secondary level experimental studies that incorporate specific variables pertinent to a particular case and supplement the established theory presented in the published literature. Such studies enable a better understanding of the specific forensic context and thus allow more accurate collection, analysis and interpretation of the trace physical evidence to be achieved.This paper presents two cases where the findings of secondary level experimental studies undertaken to address specific issues particular to two forensic investigations proved to be important. Specific pre-, syn- and post-forensic event factors were incorporated into the experimental design and proved to be invaluable in the recovery, analysis and in achieving accurate interpretations of both soil evidence from footwear and glass trace evidence from a broken window.These studies demonstrate that a fuller understanding of the specific context within which trace physical evidence is generated and subsequently collected, as well as an understanding of the behaviour of certain forms of trace physical evidence under specific conditions, can add evidentiary weight to the analysis and interpretation of that evidence and thus help a court with greater certainty where resources (time and cost) permit.     

Persistence of transferred fragrance on fabrics for forensic reconstruction applications

It has recently been established that volatile organic compounds (VOCs) successfully transfer between clothing even with a short contact of 10 s, highlighting the potential to use VOCs in forensic reconstruction scenarios, such as sexual assault cases. The mid and low volatility compounds transferred in greater amounts than high volatility compounds. This study presents empirical data addressing the persistence of transferred VOCs on clothing for the first time. A series of experiments were carried out to determine the persistence of VOCs on clothing for time periods of up 4 weeks, on natural and synthetic fibres, and at three different environmental temperatures. The data indicate that the highest VOC amounts are generally obtained for shorter persistence times of up to 1 d. Whilst high volatility compounds were not recovered in sufficient amounts to allow quantification, the four other transferred VOCs were successfully quantified for persistence times of up to 4 weeks. The persistence for mid-volatility compounds follows decay curve trends in line with those previously obtained for fibres, glass and pollen. When comparing the persistence of VOCs on a natural and a synthetic fibre, for a persistence time of 1 h, the transferred VOCs were retained on a natural fibre in higher amounts than on a synthetic fibre. However, for longer persistence times the concentration of VOCs was similar between the two fabrics. Lastly, lower environmental temperatures resulted in higher recoveries for most VOCs, especially for short persistence times. These findings demonstrate that optimal recovery of VOCs from clothing occurs when the fabric is kept at cooler temperatures and analysed soon after the fragrance transfer occurred, although VOC recovery was possible at higher temperatures and after longer persistence times. Given the transfer and persistence characteristics of VOCs from fragrance, there is potential for fragrance to be used as a form of trace in forensic reconstruction approaches.     

Detection of Diatoms by a Combination of Membrane Filtration and Transparentness,

Diagnosis of drowning remains a difficult issue in current forensic sciences. A large number of diatoms were lost by removing the supernatant after centrifugation in the conventional forensic diatom test. We developed a novel membrane filtration method to enrich diatoms from samples. A new solution using different ratios of acetic acid and eugenol is prepared to make the membrane transparent. These processes allow the diatom‐containing membrane to be visualized and identified easily by light microscopy. The tissues contaminated by water rich in diatoms were detected by the new method for the recovery of diatoms. Eleven drowning cases were analyzed by both the new method and the conventional method to compare the sensitivity of both methods. The recovery of the novel diatom test method was 54.2 ± 23.1%. The positive rate of the novel method has been proven to be superior to the conventional method in the diagnosis of drowning.     

The reincorporation and redistribution of trace geoforensic particulates on clothing: An introductory study

Two experimental studies were undertaken to investigate the processes of reincorporation and redistribution of trace evidence on garments when worn by a suspect or a victim (reincorporation) or after the garments have been seized and packaged for subsequent forensic analysis (redistribution). The first experiment utilised UV powder, an established proxy for geoforensic trace particulates and the second experiment utilised daffodil pollen transferred onto garments under conditions that mimicked forensic reality. It was demonstrated that reincorporation of trace particulates occurs from upper to lower parts of the same garment and also from upper garments to lower garments. Reincorporation also occurred to all areas of the lower garments, however the highest concentration of particulates was found to be the lap area of the jeans. Particulates also tended to be preserved around technical details such as stitching or relief design features of the garments. Thus the decay of particulates after a contact has been made does not necessarily involve a loss of those particulates from the entire system. These findings have implications for the interpretation of trace evidence when seeking to establish the source of initial contacts or the chronology of pertinent events. The second study demonstrated that folding and packaging items of clothing leads to a redistribution of any trace particulate evidence that is present thereby eliciting an alteration in the spatial distribution of that evidence. There is therefore a necessity to take the context of trace evidence into account and also to follow protocols that are sensitive to these aspects of trace evidence behaviour as a failure to do so may have consequences for the correct interpretation of such evidence.     

辽宁清河、棋盘山两座水库中硅藻种群及数量变化规律的法医学研究

目的研究辽宁清河、棋盘山两座中小型水库中硅藻种群及数量可能存在的区域性和时间性差异,拟为法医相关检案明确死因、规范现场水样提取方法及正确分析落水地点提供科学依据。方法选择辽宁境内棋盘山秀湖和铁岭清河两座水库作为研究对象,2012年春季（5月）及夏季（8月）分别在水库最宽段从岸边向水库中心以一定间距设点取样,观察硅藻种群及数量的变化。结果硅藻数量由岸边向水库中心呈现最低-增多-最多-减少-稳定的变化趋势,岸边硅藻数量最少,近岸带硅藻数量达峰值,之后硅藻数量降低,经一段水域过渡之后在水库中心区域硅藻数量趋于稳定;同一观测点春季硅藻数量明显多于夏季;岸边及近岸带以羽纹纲硅藻为主,在过渡区域,中心纲硅藻与羽纹纲硅藻混杂出现,水库中心区域内中心纲硅藻占绝对优势。结论水库型静水水体中,硅藻种群和数量存在区域性及时间性差异,合理布点取水,对于比对和分析现场水样与死者脏器中硅藻种群及数量至关重要。     

溺死鉴定中硅藻检验的应用

在法医学检案中,溺死诊断以及入水地点的判定一直是重点和难点之一,硅藻检验被认为是一种相对可靠的诊断溺死的方法,而根据硅藻的群落特征推断其入水区域具有一定的可信度。对不同水域内硅藻进行研究,可为溺死鉴定及入水区域的判定提供参考。本文就硅藻相关的生物学特性、检验方法等相关的国内外研究进展进行综述,供法医学工作者在相关科研和检案实践中参考。     

A new molecular approach to help conclude drowning as a cause of death: Simultaneous detection of eight bacterioplankton species using real-time PCR assays with TaqMan probes

We developed a novel tool for concluding drowning as a cause of death. We designed nine primer pairs to detect representative freshwater or marine bacterioplankton (aquatic bacteria) and then used real-time PCR with TaqMan probes to rapidly and specifically detect them. We previously cultured the genus Aeromonas, which is a representative freshwater bacterial species, in blood samples from 94% of victims who drowned in freshwater and the genera Vibrio and/or Photobacterium that are representative marine bacteria in 88% of victims who drowned in seawater. Based on these results, we simultaneously detected eight species of bacterioplankton (Aeromonas hydrophila, A. salmonicida; Vibrio fischeri, V. harveyi, V. parahaemolyticus; Photobacterium damselae, P. leiognathi, P. phosphoreum) using three sets of triplex real-time PCR assays and TaqMan probes labelled with fluorophores (FAM, NED, Cy5). We assayed 266 specimens (109 blood, 157 tissues) from 43 victims, including 32 who had drowned in rivers, ditches, wells, sea or around estuaries. All lung samples of these 32 victims were TaqMan PCR-positive including the lung periphery into which water does not readily enter postmortem. On the other hand, findings in blood and/or closed organs (kidney or liver) were PCR-positive in 84% of the drowned victims (except for those who drowned in baths) although the conventional test detected diatoms in closed organs in only 44% of the victims. Thus, the results of the PCR assay reinforced those of diatom tests when only a few diatoms were detectable in organs due to the low density of diatoms in the water where they were found. Multiplex TaqMan PCR assays for bacterioplankton were rapid, less laborious and high-throughput as well as sensitive and specific. Therefore, these assays would be useful for routine forensic screening tests to estimate the amount and type of aspirated water.     

The Diagnostic Value of Quantitative Assessment of Diatom Test for Drowning: An Analysis of 128 Water‐related Death Cases using Microwave Digestion‐Vacuum Filtration‐Automated Scanning Electron Microscopy

The value of diatom test for the diagnosis of drowning remains controversial. The conventional forensic diatom test with low sensitivity is not a useful tool to provide accurate information about diatom in the tissues and organs. To improve the sensitivity of the diatom test, we developed a novel method called the Microwave Digestion‐Vacuum Filtration‐Automated Scanning Electron Microscopy (MD‐VF‐Auto SEM) method which resulted in a high recovery of diatoms. In this article, we analyzed 128 water‐related death cases. Our results showed that the MD‐VF‐Auto SEM method could achieve a much higher positive rate (0.97) in drowning cases. Large amounts of diatoms are retained, even concentrated, in the lung tissues during the intense breathing movement in drowning process. This might be useful for the diagnosis of drowning. Our research indicates that the MD‐VF‐Auto SEM method would be a valuable methodology in the study of diatom test for the forensic community.     

Screen-printing ink transfer in a sexual assault case

Yellow plastic-like particles were discovered on the clothing and body of a sexual assault victim. These particles were later associated to an athletic jersey with flaking yellow screen-printed numbers and letters, worn by the suspect. Depending on its intended substrate, screen-print ink can vary in color and composition. Particles dislodged from screen-printed garments may exhibit fabric impressions. Screen-printed clothing, commonly encountered in forensic casework, should be viewed as a potential source of trace evidence.     

Trace DNA: a review,discussion of theory,and application of the transfer of trace quantities of DNA through skin contact

Advances in STR PCR DNA profiling technology allow for the analysis of minute quantities of DNA. It is frequently possible to obtain successful DNA results from cellular material transferred from the skin of an individual who has simply touched an object. Handling objects, such as weapons or other items associated with a crime, touching surfaces, or wearing clothing, may represent sufficient contact to transfer small numbers of DNA bearing cells, or trace DNA, which can be successfully analyzed. With this minimal amount of contact required to yield a suspect profile comes tremendous crime solving potential, and a number of considerations for prudent application, and the maximization of evidentiary value. Evidentiary materials not previously considered must be recognized and preserved, and the resulting DNA type profiles interpreted in their proper forensic context.     

德州市水域中硅藻分布的研究

目的研究德州市水域中硅藻分布的特点,建立德州市春季和夏季的各水域硅藻数据库。方法对德州市主要水域的130个取水地点进行春季和夏季两次采样,用强酸消解-真空抽滤-扫描电镜法检测各水域中硅藻的种属及含量,统计分析水域中硅藻含量、群落组成、相对丰度和优势种属特点。结果夏季的硅藻含量高于春季的硅藻含量,河流两个季节硅藻含量无统计学显著差异(P>0.05),湖泊和水库两个季节硅藻含量存在统计学差异(P<0.05)。各水域之间硅藻含量存在差异,含量最高为608020个/10mL,最少为10个/10mL。各水域之间种属组成、优势种属和种属优势率存在差异。结论德州地区不同水域、不同季节的水中硅藻种属和含量具有明显的特异性;建立硅藻数据库和掌握本地区水域中硅藻种属特点,有助于德州市水域内水中尸体案件硅藻的检验和落水地点的判断。     

硅藻定量检验和种属鉴定的实验研究

本实验用家兔18只,分为溺死组、死后(抛尸)入水组及对照组,每组各6只。采用消化—光镜法作肺、肝、肾硅藻计数(定量)及种属鉴定检验,同时作水样检验及空白对照。结果:(一)进一步证实生前硅藻可经空气源性进入肺脏并存积于大循环内脏(肝、肾)的概念;(二)提示水中尸体肺脏如有大量硅藻检出,仅此即可作为诊断溺死的可靠依据;空气源性吸入及检验过程中的污染并不影响该检验结果对鉴定溺死的判断。种属分析溺死组肺与水样的主要硅藻种属相符,而肝、肾中硅藻计数及种属分析均无诊断意义。     

沈阳市内浑河河段中硅藻数量及种群变化规律

目的观测沈阳市内浑河河段中硅藻数量及种群的变化规律,为法医学溺死鉴定及判断落水地点提供技术帮助与科学证据。方法 2011年全年对沈阳市内浑河河段布观测点,每月采集水样并观测硅藻数量及种群的变化规律,每周采集水样并观测硅藻优势种群的变化规律。结果沈阳市内浑河河段中硅藻数量、种群及优势种群均随时间、地点而变化;硅藻数量及种群数12~2月最低,之后逐渐升高,5月达高峰,略有下降10月达第二高峰期,之后迅速减少;硅藻优势种群4~11月同一采样点相邻两周间变化明显,7~8月同一周内不同采样点变化不明显。结论河水中硅藻变化规律复杂,受环境、水文等多种因素影响,在法医学溺死鉴定及落水地点推断过程中,应充分考虑硅藻数量及种群的变化规律。     

The individuality of fibres used to provide forensic evidence--not all blue polyesters are the same.

Fibres used in forensic casework suffer from a disadvantage common to other forms of trace evidence--it is not possible to state with absolute certainty that they originate from a specific source. Target fibre studies, population studies and research on 'blocks of colour' have effectively demonstrated the polymorphism of textile fibres (particularly man-made ones) and have shown that when a fibre is believed to have a specific putative source, the chance that it has originated from a different source purely by coincidence is extremely remote. A study by Houck MM (Houck MM, Inter-comparison of unrelated fibre evidence. Forensic Science International 2003; 135: 146-149) has shown that no coincidental matching fibres were recovered from items of clothing examined in 20 unrelated crimes. The study involved over two million comparisons. This work goes a step further, and using the example of blue polyester fibres shows that even within a very narrow segment of the whole general fibre population, many examples of a specific colour/type of man-made fibre taken from random sources can be compared and the chance of any two being the same is very low. These studies should help to show the specificity and value of transferred fibres in providing forensic evidence.