An innovative transfer DNA experimental design and qPCR assay to identify primary,secondary, and tertiary DNA transfer

“Touch DNA” is a form of trace DNA that is presumed to be deposited when an individual touches something and leaves behind DNA-containing skin cells, sweat, or other fluids. While touch DNA is often the result of direct contact (i.e., primary transfer), it can also be indirectly transferred between surfaces or individuals (e.g., secondary or tertiary transfer). Even experts cannot distinguish between different types of transfer and do not fully understand which variables affect direct versus indirect transfer or how often each type of transfer occurs. In this study, we utilize an innovative protocol that combines a paired male and female transfer DNA experimental design with an Amelogenin qPCR assay to generate data on primary, secondary, and tertiary DNA transfer. We report frequencies of indirect DNA transfer and also investigate the potential effects of participant age, self-identified ethnicity, and skin conditions on DNA transfer. Out of 22 experimental trials, we detected primary transfer (male + female) in 71% of trials, secondary DNA transfer in 50% of trials, and tertiary DNA transfer in 27% of trials. No significant associations were found between primary DNA transfer and age, self-identified ancestry, or skin conditions, however, all individuals with sloughing skin conditions demonstrated primary DNA transfer and we suggest this variable be explored in larger samples. These results contribute to a better understanding of the conditions under which secondary and tertiary DNA transfer occurs and can be used to propose realistic DNA transfer scenarios in court cases.     

A study of DNA transfers onto plastic packets placed in personal bags

The ability to detect low level DNA brings with it the uncertainty of whether the detected DNA is a result of transfer. To address this uncertainty, a simulation study was conducted in which a mock illicit drug packet was placed into the personal bags of individuals. When the average transit time of the packets was increased from around 2 h to more than 14 h, the percentage of the DNA profiles recovered from the packets which could be attributed to the individuals increased greatly from 5.3% to 48.6%. We found that drug packers who were poor shedders could not be included as contributors to the DNA profiles from the drug packets at all and there was a higher chance that individuals other than themselves could be included as contributors to the DNA profile recovered from drug packets. We also found that it was equally likely that the drug packers who had direct contact with the drug packets and bag owners who did not, could be included as contributors to the DNA profiles recovered from the packets. The results in this study highlight the importance of taking into consideration the transit time of drug packet, the shedder status of the alleged packer and the history of an item, when evaluating DNA evidence in the context of illicit drug activities.     

2,4,6-Tri(2′-pyridyl)-1,3,5-triazine for determination of iron(II), Iron(III), and total iron contents on human palms

When iron-based tools, such as knives or guns, are held, traces of iron can transfer to the skin. However, no previous studies have been published regarding the effect of the elapsed contact time on the transfer of iron species with different valences to the palm. Compared with 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine (PDT), 2,4,6-tri(2′-pyridyl)-1,3,5-triazine (TPTZ) was found to exhibit a higher sensitivity to iron(II) spectrophotometrically. This work employed 2,4,6-tri(2′-pyridyl)-1,3,5-triazine (TPTZ) and UV spectrophotometry to determine the amounts of iron(II), iron(III), and total iron transferred to human palms from iron tools. It was found that the palmar moisture level was an important factor in determining the amounts of total iron, including iron(II), transferred to the palm. For identical contact times, the amounts of total iron transferred to the palm was proportional to the palmar moisture, and the difference between the maximum and minimum amounts was 12 μg per hand. However, the amounts of iron(II) transferred to the palm gradually decreased over time for low palmar moisture levels, but steadily increased over time for high palmar moisture levels. Additionally, for average levels of palm moisture, the amounts of iron(II) and iron(III) transferred to the palm gradually decreased and increased, respectively, with longer contact times. Notably, this research could serve as a theoretical basis and guide for the detection of trace iron species with different valences on human palms for criminal investigations.     

A quantitative assessment of the extent and distribution of textile fibre transfer to persons involved in physical assault

Knowledge of the number of fibres transferred during a particular activity is essential for the interpretation of findings in similar criminal cases. In this regard, violent contacts and physical assaults still present a challenge, due to a lack of robust published data. Hereby, we present the outcome of an empirical study where different assault activities were simulated by a Jiu Jitsu team and participants were asked to play either the role of an aggressive ‘assailant’ or a defensive ‘victim’, wearing cotton garments (i.e., Gi’s). Four different scenarios were simulated in replicates (n = 5), each of them involving different intensity levels (low and high) and duration times (30 and 60 s). Results showed that approximately 1,000 to 44,000 fibres were cross-transferred between the participants’ garments, with noticeable differences between the different scenarios. These values were significantly larger than those published in previous studies and, therefore, suggested the possibility of a current underestimation of the number of fibres transferred in physical assaults. Furthermore, statistical analysis by ANOVA indicated that the all the variables tested (i.e., intensity level, duration time, and participants role) had a significant effect on the number of transferred fibres (p < 0.001) and, consequently, that some knowledge of the case circumstances may be important to make more educated estimations. This is the first time that such a methodology has been applied for the quantitative assessment of fibre transfer between participants in assault activities. Data are expected to help practitioners with the interpretation of findings in real casework and lead to a more robust evidential assessment.     

Could Secondary DNA Transfer Falsely Place Someone at the Scene of a Crime?,

The occurrence of secondary DNA transfer has been previously established. However, the transfer of DNA through an intermediary has not been revisited with more sensitive current technologies implemented to increase the likelihood of obtaining results from low‐template/low‐quality samples. This study evaluated whether this increased sensitivity could lead to the detection of interpretable secondary DNA transfer profiles. After two minutes of hand to hand contact, participants immediately handled assigned knives. Swabbings of the knives with detectable amounts of DNA were amplified with the Identifiler^® Plus Amplification Kit and injected on a 3130xl. DNA typing results indicated that secondary DNA transfer was detected in 85% of the samples. In five samples, the secondary contributor was either the only contributor or the major contributor identified despite never coming into direct contact with the knife. This study demonstrates the risk of assuming that DNA recovered from an object resulted from direct contact.     

手部脱落细胞DNA转移及二次转移的实验研究

目的研究脱落细胞遗留者洗手时间及所接触客体类型对手部脱落细胞转移的影响,同时考察手部脱落细胞DNA是否能够发生二次转移。方法 9名志愿者在洗手后30min、2h、6h分别握持木柄螺丝刀、橡胶柄螺丝刀、胶木插头1min和佩戴粗纱手套15min,对上述物品进行DNA提取检测,同时进行手部脱落细胞的二次转移实验。结果从志愿者接触过的物品中能够获得的STR基因座数量随着接触者洗手后时间的延长而增加;在洗手后30min和2h的触摸实验中,4种客体检出的基因座数量存在统计学差异,从手套中检出的基因座数量多于从木柄和橡胶柄螺丝刀中检出的数量;从脱落细胞遗留状态较差者握持过的螺丝刀中,检出了与该物品没有直接接触的脱落细胞遗留状态较好者部分STR基因座。结论接触者最后一次洗手时间是影响脱落细胞DNA转移的一个重要因素,在接触性DNA的提取检测和结果解释过程中,对有可能发生的二次转移现象应予以高度注意。     

Transfers from prison to hospital under Sections 47 and 48 of the Mental Health Act between 2011 and 2014

In England and Wales, prisoners with mental disorder of such severity as to warrant inpatient treatment may be transferred to hospital under the Mental Health Act. UK Government guidance recommends that this process should be completed within 14 days; however, evidence suggests that in many cases it can take much longer. This retrospective service evaluation of 64 male prisoners, who were transferred under Section 47 or Section 48, aimed to evaluate transfer durations. The mean time from referral to admission was 76 days. Prisoners with a psychotic disorder were admitted more quickly. Remand prisoners were admitted more quickly than sentenced prisoners. Findings suggest that, in the UK the transfer time of prisoners under Sections 47 and 48 of the Mental Health Act continues to far exceed the 14-day target which raises concern about equivalence of care for prisoners. Our findings support arguments for fundamental amendments to the admissions process.     

论海域使用权创设制度的立法完善

《海域使用管理法》建立了“审批为主、招标拍卖为辅”的海域使用权创设方式,以及“颁发海域使用权证书并向社会公告”的海域使用权公示制度。这一海域使用权创设方式存在缺陷,应该从以下四个方面予以完善：限制行政审批、鼓励竞争出让;允许以挂牌和协议方式出让;规定海域使用权出让合同;以登记时间作为海域使用权取得时间。     

乡村振兴与农地流转体制机制创新研究——基于地权配置的视角

“乡土中国”是我国农村的基本社会事实。土地问题是农村经济体制改革的逻辑起点,也是深化改革的关键着力点。优化地权配置,通过土地流转提高农地利用效率是乡村振兴战略的核心。从地权配置角度切入,剖析乡村振兴与农地流转之间的内生关系,探究了当前农地流转的成绩、不足以及困境,以图耦合地、人、业、钱等要素的关系。为推进农地流转体制机制创新,应当加快法律法规体系建设,建立健全网络化的农地流转市场并充分监管农地用途,合理界定相关权利主体及其行为边界,激活土地的多层次权能,促进现代农业与小农户有机衔接,同时健全社会保障体系,减少农地流转的后顾之忧,殷实农民获得感。     

科技成果转化和技术转移的比较及其政策含义

科技成果转化和技术转移是两个互相渗透互相包容的概念,该文通过对这两个概念内涵的比较,揭示了中国和西方相关科技法律和政策的差异,指出了中国在市场经济条件下坚持科技成果转化工作的必要性及努力方向。