The recovery of fibres from non-textile items using a static charge

This study investigated a new method of fibre recovery from non-textile items using polystyrene rods which have a static charge. A range of natural and man-made fibres were used on a number of substrates, including weapons, paper and plastic bags. The average recovery rate from all substrates was 99.1%. The effect of humidity on fibre recovery was also studied and it was found to reduce the ability of the rods to recover fibres. However this is unlikely to be an issue if recovery takes place in a forensic laboratory. It was concluded that the rods would prove a beneficial addition to the forensic laboratory as a relatively quick method of fibre recovery from non textile items where the standard method of recovery using tape lifts cannot be used.     

Blocks of colour IV: the evidential value of blue and red cotton fibres.

Samples of blue and red cotton fibres were examined using light and fluorescence microscopy as well as UV/VIS microspectrophotometry and fluorescence microspectroscopy. The degree of fluorescence and spectral variation was recorded. Particular attention was paid to the recurrence of certain spectral patterns. The importance of spectral information in the UV range is emphasized again. Colour plays a critical role in the comparison of cotton fibres in forensic sciences. Normally, fibres producing spectral patterns that are frequently seen will tend to have a lower evidential value in criminal cases as the choice of putative sources is theoretically greater and vice versa. Besides black cotton, blue and red cotton fibres are very frequent in fibre casework. The very high discriminating power using a combination of light microscopy, fluorescence microscopy and UV/VIS microspectrophotometry shows that even blue and red cotton fibres can provide excellent evidence when involved in fibre transfer cases.     

The population of coloured fibres in human head hair.

In 2002 a population study of textile fibres in human hair was carried out using 26 volunteers in Cambridgeshire, UK. Over 12,000 fibres were recovered from a variety of hair lengths using low adhesive tape and classified according to colour, generic type and fibre length. The results of the study showed that the most common fibre colours were black/grey (48%), blue (29.1%) and red (12.7%), the least common being green, orange/brown and yellow which each accounted for less than 5% of the total. Natural fibres (mainly cotton) were predominant (72.3%) and man-made fibres were considerably less frequent. When colour and generic type were classified together, the most common combinations were black and blue cottons. The least common were the man-made fibre/colour combinations with the most frequent of these accounting for less than 7% of the sample. Fibre loads carried by long hair were found to be significantly less than that carried by short hair. The results of this study are in accordance with previous fibre population studies using other types of recipient surfaces and are likely to be influenced by factors such as seasonal and geographical variation.     

A study in relation to the random distribution of four fibre types on clothing (incorporating a review of previous target fibre studies).

A new target fibre study was undertaken building upon eight previous published studies, which are reviewed here. Fifty-eight items of outer clothing, obtained from households across England, were taped and searched for three types of commonly occurring fibres and one less common fibre type. The tapes were examined using a combination of automatic and manual searching. Any fibres similar to the target fibres were removed and examined using microspectrophotometry, comparison microscopy, thin layer chromatography (TLC) and fourier transform infrared spectroscopy (FTIR) where applicable. One polyester fibre, four acrylic fibres and eleven wool fibres were found that matched the three commonly occurring target fibre samples. None of the less common polyester fibres were found. One item had six matching wool fibres and another had the polyester fibre and an acrylic fibre recovered from it. The remaining eight fibres were each recovered from individual items. The results suggest that finding a large number of fibres that match a control is unlikely to happen by chance, which supports the findings of the previous target fibre studies.     

The population of coloured textile fibres in domestic washing machines.

A population survey was carried out to analyse examples of the coloured fibre population that may be expected to exist in both front- and top-loading domestic washing machines during Spring, in Sydney, Australia. White cotton T-shirts were washed both individually, and with a normal household wash load, then taped to recover extraneous fibres transferred during the wash cycle. Twelve thousand one hundred and seventy-eight fibres were classified according to length, colour and generic class. Cotton fibres were most prevalent (69.4%), followed by man-made fibres (24.2%). The most common colour/generic class combinations were black/grey cotton (27%), blue cotton (20%) and red cotton (15.6%). Other combinations generally represented under 2% of the total fibre population. Two thirds (65.9%) of the recovered fibres were under 2 mm in length, the proportion of fibres decreasing with increasing fibre length. Variations in machine type did not affect the distribution of fibres with respect to fibre type, colour or length.     

The analysis and comparison of blue wool fibre populations found at random on clothing.

Fifty-eight garments were taped and searched for mid to dark blue wool fibres. These were then removed from the tapings, mounted on slides and examined using a high-power microscope (400x). A total of 2,740 blue wool fibres were identified and visible range microspectrophotometry (MSP) was performed on them. Three hundred independent blue wool populations were identified on 56 of the 58 garments searched. The lack of control fibres meant the spectral range of each population was unknown. The number of populations may have been underestimated by grouping together the fibres that had broad single peaks and a lack of distinguishing features in the spectra. Although blue wool is considered to be a common fibre type, 300 unique spectral shapes were identified by the use of microspectrophotometry alone. This demonstrates that the dyes used in the dyeing of blue wool are variable. Showing that many different populations of blue wool occur on a range of garments should ensure that the forensic scientist does not underestimate or understate the strength of evidence in cases where blue wool is found. Hopefully this work will enlighten scientists and enable them to also assess the true value of their findings when other commonly occurring fibres are encountered.     

The effect of tape type,taping method and tape storage temperature on the retrieval rate of fibres from various surfaces: An example of data generation and analysis to facilitate trace evidence recovery validation and optimisation

This paper aspires to assist those tasked with data generation and analysis for the purpose of the validation and/or optimisation of trace evidence recovery. It does so via a detailed report of the authors’ approach to this problem in the context of target fibre retrieval using self-adhesive tapes.Textile fibres can provide valuable evidence at both source and activity levels. This ability stems from their near ubiquity in the man-made environment, their potential for high levels of discrimination (especially when found in combination) and their reproducible transfer and persistence behaviours. To realise this value for the criminal justice system, it is vital that police forces and forensic providers are collectively able to search for, recover and analyse fibres found at crime scenes and correctly evaluate their evidential value.ISO accreditation provides quality assurance for such activities. The work reported in this paper was part of a study to validate crime scene fibre retrieval processes for the purposes of ISO17020 accreditation. However, it is hoped that it will be of assistance to those wishing to validate and/or optimise forensic fibre recovery whether at the crime scene or in the laboratory. Further, the methods described may be of value to those who need to validate and/or optimise the recovery of other types of trace evidence.This paper outlines a series of experiments that investigated the effect of four factors on the rate at which target fibres could be recovered from surfaces by tape lifting. The factors were tape type (with two levels, namely: J-LAR and Crystal Tabs), tape storage temperature (three levels: −5 °C, room temperature [19 ± 1 °C] and 35 °C), taping method (two levels: zonal and one-to-one) and surface (12 levels: each being a surface type commonly encountered at crime scenes). This resulted in 144 unique experimental conditions. For each of these, five repeat fibre recovery rate determinations were carried out, generating 720 data points. All surfaces were clean and dry prior to target fibres being transferred and recovered. In all cases, the tapes were applied to the surfaces at 19 ± 1 °C.These experiments showed that the surfaces can be divided into three stable clusters based on the median and interquartile range of the fibre retrieval rate achieved from each of them. Also, they showed that, in terms of the proportion of the target fibres retrieved, typically and setting aside interaction effects:

• •Crystal Tabs outperformed J-LAR;
• •rolls of tape stored at −5 °C and 35 °C outperformed those stored at room temperature;
• •one-to-one taping outperformed zonal taping.

However, notably, a good degree of between-condition overlap was also apparent in the data. To understand this, a four-way factorial ANOVA model was built which revealed significant and substantive effects for all four main effects and for 10 of the 11 interactions. Importantly, the four-way interaction term was amongst those found to be significant. The interplay between the effects of the four factors was analysed by means of simple effects tests and pairwise contrasts. Tables and interactive parallel coordinate plots have been created. Using these it can easily be seen which of any given pair of levels of each of the four factors resulted in the higher fibre retrieval rate under any one of the unique conditions of the study, and the effect size and statistical significance of this observation.Qualitative evaluations of the effect of tape storage temperatures on tape pliability and its propensity to tear in use were also made.     

A textile fibre survey as an aid to the interpretation of fibre evidence in the Sydney region.

Frequency figures of the fibre population on textile cinema seats were measured in Sydney, Australia, in winter. Sixteen seats were analysed from a very popular cinema complex, with 3025 fibres classified according to colour, generic class and fluorescence properties (100 grey-black cotton fibres only). The recovered fibres were mostly natural fibres (84%) with cotton the most common generic type (70%). On the contrary, man made fibres were relatively rare (15%) with rayon constituting the majority of these (51%). The most common colour/generic class combinations were grey-black cotton (33%) and blue cotton (30%) accounting for 63% of the total population. All other frequencies were below 5%, most below 1% using only the two properties of colour and generic class. Fluorescence properties were found to be very discriminating as far as grey-black cotton fibres were concerned. These features are considered and discussed and in particular, to emphasise the significance of fibres as evidence of contact.     

Polymorphic sites in human mitochondrial DNA control region sequences: population data and maternal inheritance

Sequence analysis of the mitochondrial DNA (mtDNA) control region is of central importance for forensic identity testing as well as for studies of human evolution. Here we report the sequencing data of the hypervariable regions I and II from 50 unrelated individuals from a western German population (Rhine area). In regions I and II, 52 and 26 sites of sequence polymorphism, respectively, were noted. Nucleotide substitution rather than insertion/deletion was the majority of variation. The distribution showed a large bias towards transitional changes than transversional changes. Furthermore we investigated uniparental inheritance in seven CEPH families each family with 7–9 maternal descendants. Most maternal relatives shared identical mtDNA sequences. Additionally sequences were compared for father:child pairs and as expected no evidence for paternal transmission of mtDNA was observed. The high variability of mtDNA control region sequences permits utility in forensic identity investigations. The data also indicate that the neomutation rate seems to be very low from one generation to the other.     

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.     

Population distribution of six PCR-amplified loci in Madeira Archipelago (Portugal).

Frequency data of the short tandem repeat (STR) loci HUMTH01, HUMVWA31/A, HUMF13A1, HUMFES/FPS, D12S391 and HUMFIBRA/FGA were determined in blood stains obtained from a population of unrelated individuals from the Madeira Archipelago. The observed genotype distribution showed no significant deviation from the Hardy-Weinberg equilibrium and there was no evidence for association of alleles among the six loci. Population data showed a combined discrimination power of 0.9999998 and a chance of exclusion of 0.99597. The frequencies are similar to those of other compared caucasian populations but significant differences were found between the Madeira population and Japanese, Chinese, Greenland Eskimos and Quechua Amerindians. The six loci studied, together proved to be highly discriminating and valuable for forensic cases.     

A fresh scientific look at transfer and persistence: From a materials science and tribology perspective

Knowledge of the mechanisms governing transfer, persistence, and recovery of trace evidence, together with background prevalence in the population of interest, and other task relevant information, is key for the forensic interpretation and reconstruction of what happened at the activity level. Up to now, this informational “toolkit” has largely been developed through empirical forensic studies on specific trace materials such as glass, textile fibers, and soil. Combined with the identified systemic siloing between disciplines, while valuable, such research tends to be very material-dependent, introducing specific parameters and interpretations that may have actually impeded the recognition of underlying foundational factors applicable to most material types. In Australia, there has been a renewed interest in developing a discipline-independent framework for the interpretation and/or reconstruction of trace evidence to interpret specific circumstances in casework. In this paper, we present a discipline agnostic “way of thinking” that has been anchored in foundational science underpinning the trace evidence discipline. Physical and mechanical material properties such as material geometry and surface topography, strength, stiffness, and hardness collectively influence contact interactions through underlying friction, wear, and lubrication cause and effect mechanisms. We discuss how these fundamental factors and parameters stemming from materials science and tribology may be adopted and adapted by forensic practitioners and researchers to contribute to a better understanding of transfer, persistence, and recovery mechanisms irrespective of evidence discipline and material type. Examples are provided to demonstrate the practical significance to real-life casework and academic research.     

Human Leukocyte Antigen alleles as an aid to STR in complex forensic DNA samples

Human biological samples with multiple contributors remain one of the most challenging aspects of DNA typing within a forensic science context. With the increasing sensitivity of commercially available kits allowing detection of low template DNA, complex mixtures are now a standard component of forensic DNA evidence. Over the years, various methods and techniques have been developed to try to resolve the issue of mixed profiles. However, forensic DNA analysis has relied on the same markers to generate DNA profiles for the past 30 years causing considerable challenges in the deconvolution of complex mixed samples. The future of resolving complicated DNA mixtures may rely on utilising markers that have been previously applied to gene typing of non-forensic relevance. With Massively Parallel Sequencing (MPS), techniques becoming more popular and accessible even epigenetic markers have become a source of interest for forensic scientists.The aim of this review is to consider the potential of alleles from the Human Leukocyte Antigen (HLA) complex as effective forensic markers. While Massively Parallel Sequencing of HLA is routinely used in clinical laboratories in fields such as transplantation, pharmacology or population studies, there have not been any studies testing its suitability for forensic casework samples.     

A comparison of efficiency of manual and automatic fibres search with the Maxcan fibre finder

The aim of this work was to study the efficiency of automatic fibre searching with the Maxcan fibre finder (Cox Analytical Systems, Sweden) in comparison to manual searching. The influence of some parameters (color, thickness, background noise) on the results of a fibre search was considered. Eighteen experimental tapes with different target fibres and different background noises were prepared in the laboratory. Searching of fibres was performed manually and with the Maxcan fibre finder by different operators from four European laboratories. Two laboratories have the Maxcan fibre finder system and the two instruments were used and compared in this study. The results show that searching with the Maxcan is generally as efficient as manual searching, except for very pale or very dark fibres. Note that the tapes used for these experiments were prepared in laboratory, and are not completely representative of the tape that could be obtained in real cases. To generalize the results obtained, further research on real case samples would be necessary.     

A comparison of efficiency of manual and automatic fibres search with the Maxcan fibre finder

The aim of this work was to study the efficiency of automatic fibre searching with the Maxcan fibre finder (Cox Analytical Systems, Sweden) in comparison to manual searching. The influence of some parameters (color, thickness, background noise) on the results of a fibre search was considered. Eighteen experimental tapes with different target fibres and different background noises were prepared in the laboratory. Searching of fibres was performed manually and with the Maxcan fibre finder by different operators from four European laboratories. Two laboratories have the Maxcan fibre finder system and the two instruments were used and compared in this study. The results show that searching with the Maxcan is generally as efficient as manual searching, except for very pale or very dark fibres. Note that the tapes used for these experiments were prepared in laboratory, and are not completely representative of the tape that could be obtained in real cases. To generalize the results obtained, further research on real case samples would be necessary.     

A computerized data base of mail order garments – a contribution toward estimating the frequency of fibre types found in clothing: Part 3: The content of the data bank – is it representative?

In Part 3 of this series the authors have tried to evaluate the representativity of the Catalogue Data Base. At present this is only possible by comparing the fibre percentages obtained with figures from World Textile Production, with those of a more regional character, with existing data from alternative collections and with that from other enquiries. It is apparent that a true test for the representativity of the Catalogue Data Base is not possible. Figures which would be directly comparable do not exist. Nevertheless, it is possible to show that the most common fibre types and colours and their rank orders are the same in the different collections and production figures. The forensic value of common fibres when they appear in certain garments or combinations is presented and also the value of fibres which rarely appear in the CDB. The authors give an outlook on further activities to validate the data in the Catalogue Data Base and discuss the combination of the CDB data with that from alternative collections. Theoretical examples are presented.     

Identification of gunshot residue: a critical review

A review of the scientific papers published on inorganic gunshot residue (GSR) analysis permits to study how the particle analysis has shown its capability in detection and identification of gunshot residue. The scanning electron microscope can be the most powerful tool for forensic scientists to determine the proximity to a discharging firearm and/or the contact with a surface exposed to GSR. Particle analysis can identify individual gunshot residue particles through both morphological and elemental characteristics. When particles are detected on the collected sample, the analytical results can be interpreted following rules of a formal general interpretative system, to determine whether they come from the explosion of a primer or from other possible sources. The particles on the sample are compared with an abstract idea of "unique" GSR particle produced by the sole source of the explosion of a primer. "Uniqueness" is not the only problem related to GSR detection and identification for a forensic scientist. With "not-unique" particles interpretation of results is extremely important. The evidential strength of "not-unique" particles can increase with a more fruitful interpretative framework based on Bayes rule. For the assessment of the value of a GSR in linking a suspect and a crime, it is important to compare two hypothesis: the first can be that of the evidence if the suspect has been shooting in a specific situation, the second that of the evidence if the suspect was not involved in this shooting. This case specific or case-by-case approach is closer to what the court is interested in. The authors consider that a "case-by-case" approach should be followed whenever possible. Research of models and data such as those developed in other trace evidence material (fibres, glass, etc.) using a Bayesian approach is suggested in the interpretation of GSR.     

武汉汉族8个Y染色体双等位基因标记遗传多态性

目的筛选汉族群体中具有多态性的Y染色体双等位基因标记并研究其等位基因及单体群频率分布, 为法医学应用和群体进化研究提供基础数据。方法采用片段长度差异等位基因特异性PCR和PAGE技术对武汉地区160名男性汉族无关个体的8个Y染色体双等位基因标记(M9、M89、M111、M119、M122、M134、IMS-JST003305 和SRY+465)进行分型。结果 8个双等位基因标记在武汉汉族群体中均具有遗传多态性,其基因多样性(GD)范围为 0．0126-0．4830,共检出9种不同单体群(Hg1～9),其单体群多样性(HD)为0．7776。结论 8个Y染色体双等位基因标记组成的单体群在法医学应用和群体进化研究中具有一定的实用价值,可作为Y-STRs标记的有效补充。     

Polymorphism analysis of D19S253 locus in Guangzhou area population

Frequency data for STR system D19S253 were obtained from 105 unrelated individuals of Guangzhong population. PCR products were detected by horizontal native polyacrylamide gel electrophoresis and a total of 9 alleles were identified by side-by-side comparison with a sequenced allelic ladder prepared by ourselves. The observed genotype distribution conformed with Hardy-Weinberg equilibrium. The high information content found in this system(heterozygosity rate was 0.8353, the mean exclusion chance was 0.7499, the discrimination power was 0.9211, the polymorphism information content was 0.8203) indicated it is a useful means in forensic routine casework both in criminal and paternity cases.     

物证鉴定证据应用层级论

用物证鉴定结论证明犯罪需要经过推理过程,将物证来源鉴定结论转化为嫌疑人行为推论,后者再作为法律事实证明嫌疑人是否有罪。物证鉴定证据应用的递进证明关系,可以用由依次推理关系连接的物证来源结论层、行为推论层和定罪层构成的物证鉴定层级模型描述。该模型可直观表达和评估物证鉴定结论证据应用效力。