The transfer and persistence of automotive carpet fibres on shoe soles

The transfer and persistence of automotive carpet fibres to shoe soles was investigated. It was found that fibres were transferred with the normal activity of a car passenger. Carpet type and shoe sole parameters were significant determinants in the number of fibres that transferred. The average number of fibres was between about one and 33 per sole. Fibres that had been transferred after normal activity only persisted for a few minutes after walking. A survey of the shoe soles of people about to leave their car showed that fibres were usually present. The majority of shoe soles surveyed had less than five fibres with the greatest number of fibres found being 14. The likelihood of finding a large number of fibres on such soles is rare. Fibre composition of automotive carpets showed a high degree of variation. Grey was seen to be a common colour irrespective of the colour of the vehicle body.     

Using the Nondonor Distribution to Improve Communication and Inform Decision Making for Low LRs from Minor Contributors in Mixed DNA Profiles

The reporting of a likelihood ratio (LR) calculated from probabilistic genotyping software has become more popular since 2015 and has allowed for the use of more complex mixtures at court. The meaning of “inconclusive” LRs and how to communicate the significance of low LRs at court is now important. We present a method here using the distribution of LRs obtained from nondonors. The nondonor distribution is useful for examining calibration and discrimination for profiles that have produced LRs less than about 10⁴. In this paper, a range of mixed DNA profiles of varying quantity were constructed and the LR distribution considering the minor contributor for a number of nondonors was compared to the expectation given a calibrated system. It is demonstrated that conditioning genotypes should be used where reasonable given the background information to decrease the rate of nondonor LRs above 1. In all 17 cases examined, the LR for the minor donor was higher than the nondonor LRs, and in 12 of the 17 cases, the 99.9 percentile of the nondonor distribution was lower when appropriate conditioning information was used. The output of the tool is a graph that can show the position of the LR for the person of interest set against the nondonor LR distribution. This may assist communication between scientists and the court.     

Shedder status: Exploring means of determination

“Shedder status” or “shedder type” are commonly used terms that categorise an individual based on their ability to deposit “touch” DNA via direct contact with a surface. However, it is not yet clear how best to categorise an individual into a shedder class, or how to allocate a shedder score on a sliding scale. This study considers categorisation of participants into discrete shedder categories based on DNA quantity and profile quality data, the maintenance of their shedder status over an extended period, and explores whether different methods of deposition or collection directly from hands or other body areas are interchangeable and/or more appropriate means of determining an individual’s shedder status.The shedder categorisation of participants was possible from their handprints and remained unchanged over three years. Washing hands had limited impact and shedder categorisation was not readily possible from samples collected directly from hands, other body areas or gloves after wearing gloves for a set duration. Use of consecutive deposits may assist in establishing a participant’s shedder status. As shedder categorisation may be of relevance during activity level assessments further efforts towards the ability to do so are necessary.     

Trace evidence dynamics of cocaine on banknotes: A comparison study of paper and polymer banknotes

It is well established that a large proportion of paper banknotes in circulation contain traces of cocaine. Being able to discriminate between the innocent transfer of illicit drug particles acquired through everyday interactions with surfaces such as banknotes, as opposed to transfer resulting from criminal activities can provide valuable intelligence that can inform an investigation. With many countries adopting polymer banknotes as legal tender, it is important to consider the transfer of cocaine from these surfaces as well as the retention of these particulates on polymer banknotes for evaluative interpretation in crime reconstruction. This comparison study assessed three contact variables (force, time, and rotation) on the transfer of cocaine particulates from paper and polymer banknotes onto a human skin proxy. The persistence of cocaine particulates was assessed through a realistic scenario which mimicked a cash transaction. Quantifiable amounts of cocaine were transferred onto the human skin proxy across all of the contacts assessed, with a greater transfer observed with contacts involving polymer banknotes and those contacts which involved rotation. Following extensive handling, cocaine persisted on both banknote types, with paper banknotes retaining larger amounts of cocaine than polymer banknotes. These findings show that cocaine can persist on both paper and polymer banknotes for extended periods of time following handling and is therefore available for transfer. This transfer then readily occurs, even when contact is brief and involves relatively small forces. A key distinction between the banknote types was that cocaine particulates are more likely to transfer from polymer banknotes due to the lower retention rate of particulates on this surface. Such insights can aid in evaluating the relevance of illicit drug particles identified on items or persons of interest in crime reconstruction approaches.     

The transfer of touch DNA from hands to glass, fabric and wood

The transfer of DNA from hands to objects by holding or touching has been examined in the past. The main purpose of this study was to examine the variation in the amount of DNA transferred from hands to glass, fabric and wood. The study involved 300 volunteers (100 for glass, 100 for fabric and 100 for wood) 50% of which were male and 50% female. The volunteers held the material for 60 s. The DNA was recovered from the objects using a minitape lift, quantified using the Quantifiler kit assay, extracted using a ‘Qiagen^® QIAamp DNA mini kit’ and amplified using the AmpFlSTR^® SGM Plus™ Amplification Kit at 28 cycles. The results show that using ANOVA there was a significant difference (F = 8.2, p < 0.05) between the three object types in the amount of DNA recovered. In terms of DNA transfer and recovery, wood gave the best yield, followed by fabric and then glass. The likelihood of success of obtaining a profile indicative of the holder was approximately 9% for glass samples, 23% for fabric and 36% for wood. There was no significant difference between the amount of DNA transferred by male or female volunteers. In this study good shedder status, as defined by obtaining useful profiles of 6 or more alleles, is estimated at approximately 22% of the population. The phenomenon of secondary transfer was observed when mixed DNA profiles were obtained but the incidence was low at approximately 10% of the total number of samples. DNA profiles corresponding to more than one person were found on objects which had been touched by only one volunteer. Although secondary transfer is possible the profiles obtained from touched objects are more likely to be as a result of primary transfer rather than a secondary source.     

DIP-STR在不平衡混合DNA样本中的分析研究

当前,DNA检验技术作为打击犯罪的利器,在法医鉴定中发挥着巨大作用。但对于性侵、暴力犯罪等案件中提取的混合DNA样本,尤其是从受害人或嫌疑人的接触物上采集的高度不平衡混合DNA样本,利用常染色体STR检验方法得到的结果通常不是很理想。由于PCR扩增偏倚,从混合样本中检测出痕量DNA分型是一个巨大的挑战,也是当前法医DNA检验的一个难点。近年来的研究显示,利用新型连锁遗传标记DIP-STR,即结合缺失或插入多态性片段DIP(deletion–insertion polymorphisms)和STR的连锁位点,可以用来检测出混合DNA样本中任一性别和细胞起源的微量DNA,甚至在DNA混合比例高达1:1000时,DIP-STR标记的灵敏度、特异性仍旧相对较为理想。因此,DIP-STR标记的分析可以作为常染色体STR检验的有效补充。本文将对DIP-STR在不平衡混合DNA样本分析中的研究背景、方法及其应用前景进行综述。     

Massively parallel sequencing and the emergence of forensic genomics: Defining the policy and legal issues for law enforcement

Use of DNA in forensic science will be significantly influenced by new technology in coming years. Massively parallel sequencing and forensic genomics will hasten the broadening of forensic DNA analysis beyond short tandem repeats for identity towards a wider array of genetic markers, in applications as diverse as predictive phenotyping, ancestry assignment, and full mitochondrial genome analysis. With these new applications come a range of legal and policy implications, as forensic science touches on areas as diverse as ‘big data’, privacy and protected health information. Although these applications have the potential to make a more immediate and decisive forensic intelligence contribution to criminal investigations, they raise policy issues that will require detailed consideration if this potential is to be realised. The purpose of this paper is to identify the scope of the issues that will confront forensic and user communities.     

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.     

The detection and persistence of Cannabis sativa DNA on skin

The presence of Cannabis sativa DNA was detected on the skin of persons who have recently handled both leaf and resinous material. The persistence of C. sativa DNA was examined on the skin. The subjects were asked to either repeatedly rub their hands on their trousers, place their hands repeatedly into their pockets or wash their hands in soap and water. After rubbing the hands on trousers or placing them in pockets C. sativa DNA could still be detected. No DNA could be detected after washing the hands.     

The NucleoSpin DNA Clean-up XS kit for the concentration and purification of genomic DNA extracts: An alternative to microdialysis filtration

Traditionally, DNA extracts from biological evidence items have been concentrated and rinsed using microdialysis filtration units, including the Centricon^® and Microcon^® centrifugal filter devices. As an alternative to microdialysis filtration, we present an optimized method for using NucleoSpin^® XS silica columns to concentrate and clean-up aqueous extracts from the organic extraction of DNA from biological samples. The method can be used with standard organic extraction and dithiothreitol (DTT)-based differential extraction methods with no modifications to these methods prior to the concentration and clean-up step. Extracts from laboratory-prepared bloodstains, saliva and semen stains have been successfully amplified with both qPCR and STR assays. Finally, the total time to process a set of samples with the NucleoSpin^® XS column is approximately 30 min vs. approximately 1.5 h with the Centricon^® YM-100 filter device.     

Influence of the luminol chemiluminescence reaction on the confirmatory tests for the detection and characterization of bloodstains in forensic analysis

Preliminary tests for the detection of stains at crime scenes aim to focus the police work making them more efficient in the combat of criminality. The application of the luminol chemiluminescence reaction (3-aminoftalhidrazida) in presumptive tests for the detection of bloodstains is known for more than 40 years in forensic science. This reaction is based on the emission of light through the chemical reaction of luminol mixed with hydrogen peroxide and a hydroxide in the presence of a catalytic molecule (iron from the hemoglobin) (Laux [1]).This work evaluates the luminol interference and its effect on subsequent serological and DNA testing. Samples prepared with blood and different concentrations of luminol solution containing luminol, peroxide of hydrogen and sodium carbonate, were analyzed. Additionally, samples of serial dilutions of standard DNA mixed with luminol solution were also analyzed. Although presumptive tests with luminol do not establish the characterization and identification of stains at crime scenes, preliminary results indicated that it is suitable for the detection of invisible bloodstains for forensic analysis, with few detrimental effects on the serological tests and subsequent DNA recovery and typing.     

Following the transfer of DNA: How far can it go?

The issue of DNA transfer is becoming increasingly important in crime scene situations, as DNA analytical techniques now detect tiny amounts. Whereas primary and secondary DNA transfers have been well studied, subsequent transfer steps have received much less focus. This study aimed to measure the detectability of a DNA source after multiple transfer events. Transfer of wet blood gave a full genetic profile well beyond the secondary transfer events on both cotton and glass substrates. Dry blood gave a full profile well beyond the secondary transfer events on glass only, but to a lesser extent than wet blood. Touch DNA only produced a full profile on the primary substrate on both cotton and glass, and detectable quantities beyond the secondary transfer event on glass only. Our results will contribute to a better understanding of the tertiary and subsequent transfer of DNA, which will allow for improved evaluation of the likelihood of alternative scenarios explaining why an individual's DNA was found at a crime scene.     

Automated DNA casework workflow: A retrospective study of the first implementation of FIDL at the Netherlands Forensic Institute

FIDL is a fast and automated DNA identification line which represents a series of software solutions automating the process from raw capillary electrophoresis data to reporting. This retrospective study provides insight in the numbers of cases, turnaround time, results compared to the standard workflow and the benefits automation has in a large volume workflow.     

A novel platform for the modular integration of forensic assay setup and medium- to high-throughput purification of nucleic acids

With its extraction and assay setup modules, the QIAsymphony^® provides a highly flexible solution for processing forensic samples in a medium- to high-throughput scale. We tested the sensitivity of extraction, precision of sample processing, and accuracy of automated assay setup of this integrated system. Results attest to QIAsymphony's ability to isolate DNA from a spectrum of common forensic samples and process these samples without cross-contamination. Furthermore, accurate assay setup for downstream applications, like PCR, make this system highly suited for enhancing laboratory workflow.     

Establishing the Limits of TrueAllele® Casework: A Validation Study

The limits of the expert system, TrueAllele^® Casework (TA), were explored using challenging mock casework profiles that included 17 single‐source and 18 two‐, 15 three‐ and 7 four‐person DNA mixtures. The sensitivity (ability to detect a minor contributor) of the TA analysis process was examined by challenging the system with mixture DNA samples that exhibited allelic and locus dropout and other stochastic effects. The specificity (ability to exclude nondonors) was rigorously tested by interrogating TA derived genotypes with 100 nondonor profiles. The accuracy with which TA estimated mixture weights of contributors to the two‐person mixtures was examined. Finally, first‐degree relatives of donors were used to assess the ability of the system to exclude close relatives. TA demonstrated great accuracy, sensitivity, and specificity. TA correctly assigned mixture weights and excluded nearly all first‐degree relatives. This study demonstrates the analysis power of the TrueAllele^® Casework system.     

中国法医学会物证专业委员会法医DNA分析的若干建议

中国法医学会法医物证学专业委员会与国际法医遗传学会中文专委会于2006年10月在成都召开学术会议。我们的讨论强调有必要将国际法医遗传学会的信息及时传递到中国。因此,按照国际法医遗传学会的指南,我们推荐混合斑分析,法医DNA数据库及新遗传标记选择标准供同行参考。     

The efficiency of Y-chromosome markers in forensic trace analysis and their inclusion in the Austrian National DNA Database

Y-STR markers are a valuable tool in the analysis of biological traces in which a mixture of male and female trace material is to be expected. It is possible to generate a Y-chromosome DNA profile, even if all the prior sperm tests are negative and no sign of any male component is found in amelogenin. In 38 of a total of 239 sexual offences a perpetrator trace was identified solely using Y-STR analysis. Based on these findings, the Austrian National DNA Database was expanded to include Y-STRs in 2012 with the primary objective to identify serial sexual offences.     

Applications and extensions of subpopulation theory: a caseworkers guide

This paper extends the calculation of conditional probabilities from those given by Balding and Nichols to casework situations where a series of possible DNA types are possible. Such situations may occur when a sample is identified containing a mixture of DNA from two or more people or where extra information can be determined about the subpopulation under consideration by analysis of additional samples. Using this approach, the error in the estimated likelihood ratios is expected to reduce as the number of additional individuals typed from the subpopulation increases.     

小鼠骨骼肌细胞核DNA降解与死亡时间的关系

目的　监测小鼠死后骨骼肌核内DNA降解的情况 ,探讨死后细胞核DNA降解的一般规律。方法　建立小鼠死亡模型 ,在死后 72h内 ,以 12h的间隔取骨骼肌样本进行单细胞凝胶电泳 ,在荧光显微镜下测量彗星图像 ,并作统计学分析。结果　机体死后 ,骨骼肌细胞在电泳图像上出现了明显的彗星形拖尾 ,L/W比值随死亡时间而逐渐增大 ,二者呈一定的线性关系。结论　单细胞凝胶电泳技术可以应用于早期死亡时间推断。