Recovery efficiencies of anthrax spores and ricin from nonporous or nonabsorbent and porous or absorbent surfaces by a variety of sampling methods*

The 2001 anthrax letter cases brought into focus the need to establish the most effective environmental sampling procedures. Results are presented from two studies aimed at establishing the best procedures for everyday surfaces likely to be contaminated after the release of environmentally stable bioaggressive agents, as exemplified by anthrax spores and ricin. With anthrax spores, contact plates, with mean retrieval rates of 28-54%, performed better than other methods by a wide margin for flat nonporous, nonabsorbent surfaces. They also proved best on flat porous, absorbent materials, although recoveries were low (<7%). For both agents, dry devices (swabs, wipes, Trace Evidence Collection Filters) had universally poor retrieval efficiencies with no significant differences between them. Among moistened devices (wipes, swabs, and Sample Collection and Recovery Devices), wipes were generally best, albeit with considerable cross-over among individual readings (highest mean recoveries for anthrax spores and ricin 5.5% and 2.5%, respectively, off plastic).     

The Recovery of Latent Fingermarks from Evidence Exposed to Ionizing Radiation*

Abstract: Continual reports of illicit trafficking incidents involving radioactive materials have prompted authorities to consider the likelihood of forensic evidence being exposed to radiation. In this study, we investigated the ability to recover latent fingermark evidence from a variety of substrates that were exposed to ionizing radiation. Fingermarks deposited on common surfaces, including aluminum, glass, office paper, and plastic, were exposed to doses ranging from 1 to 1000 kGy, in an effort to simulate realistic situations where evidence is exposed to significant doses of radiation from sources used in a criminal act. The fingermarks were processed using routine fingermark detection techniques. With the exception of glass and aluminum substrates, radiolysis had a considerable effect on the quality of the developed fingermarks. The damage to ridge characteristics can, in part, be attributed to chemical interactions between the substrate and the components of the fingermark secretions that react with the detection reagents.     

Functional MRI Detection of Deception After Committing a Mock Sabotage Crime*

Abstract: Using Blood Oxygen Level Dependent (BOLD) functional MRI (fMRI) to detect deception is feasible in simple laboratory paradigms. A mock sabotage scenario was used to test whether this technology would also be effective in a scenario closer to a real‐world situation. Healthy, nonmedicated adults were recruited from the community, screened, and randomized to either a Mock‐crime group or a No‐crime group. The Mock‐crime group damaged and stole compact discs (CDs), which contained incriminating video footage, while the No‐crime group did not perform a task. The Mock‐crime group also picked up an envelope from a researcher, while the No‐crime group did not perform this task. Both groups were instructed to report that they picked up an envelope, but did not sabotage any video evidence. Participants later went to the imaging center and were scanned while being asked questions regarding the mock crime. Participants also performed a simple laboratory based fMRI deception testing (Ring‐Watch testing). The Ring‐Watch testing consisted of “stealing” either a watch or a ring. The participants were instructed to report that they stole neither object. We correctly identified deception during the Ring‐Watch testing in 25 of 36 participants (Validated Group). In this Validated Group for whom a determination was made, computer‐based scoring correctly identified nine of nine Mock‐crime participants (100% sensitivity) and five of 15 No‐crime participants (33% specificity). BOLD fMRI presently can be used to detect deception concerning past events with high sensitivity, but low specificity.     

A simple and effective image-statistics-based approach to detecting recaptured images from LCD screens

It is now extremely easy to recapture high-resolution and high-quality images from LCD (Liquid Crystal Display) screens. Recaptured image detection is an important digital forensic problem, as image recapture is often involved in the creation of a fake image in an attempt to increase its visual plausibility. State-of-the-art image recapture forensic methods make use of strong prior knowledge about the recapturing process and are based on either the combination of a group of ad-hoc features or a specific and somehow complicated dictionary learning procedure. By contrast, we propose a conceptually simple yet effective method for recaptured image detection which is built upon simple image statistics and a very loose assumption about the recapturing process. The adopted features are pixel-wise correlation coefficients in image differential domains. Experimental results on two large databases of high-resolution, high-quality recaptured images and comparisons with existing methods demonstrate the forensic accuracy and the computational efficiency of the proposed method.     

刑事现场188份接触DNA检材法医学检验分析

目的分析188份接触DNA检材的提取、送检和检验结果,探讨接触DNA检出率及可能影响接触DNA检验的因素。方法收集本辖区2016年1月至2016年10月提取并送检的188份接触DNA检材,按照检材载体性质、提取方法、送检时间、检出率等进行分类,采用SPSS13.0软件对数据进行统计分析和χ2检验。结果188份接触DNA检材成功进行STR分型的有38份,检出率为20.21%;其中表面质软、粗糙的载体接触DNA检出率58.82%,高于其它载体接触DNA检出率组的差异具有统计学意义;直接原物提取的接触DNA检材检出率42.11%,高于脱落细胞粘取器提取、棉签拭子转移提取的检出率组的差异具有统计学意义;送检时间早的检材检出率高于送检时间晚的检材组且具有统计学意义。结论接触DNA检材的检出率受载体性质、提取方法、送检时间等因素影响,日常现场勘查时要注重发现检出率高的载体上的接触DNA选择适当的方法提取,并及时送检。     

Children's Lie-Telling to Conceal a Parent's Transgression: Legal Implications

Children's lie-telling behavior to conceal the transgression of a parent was examined in 2 experiments. In Experiment 1 (N = 137), parents broke a puppet and told their children (3-11-year-olds) not to tell anyone. Children answered questions about the event. Children's moral understanding of truth- and lie-telling was assessed by a second interviewer and the children then promised to tell the truth (simulating court competence examination procedures). Children were again questioned about what happened to the puppet. Regardless of whether the interview was conducted with their parent absent or present, most children told the truth about their parents' transgression. When the likelihood of the child being blamed for the transgression was reduced, significantly more children lied. There was a significant, yet limited, relation between children's lie-telling behavior and their moral understanding of lie- or truth-telling. Further, after children were questioned about issues concerning truth- and lie-telling and asked to promise to tell the truth, significantly more children told the truth about their parents' transgression. Experiment 2 (N = 64) replicated these findings, with children who were questioned about lies and who then promised to tell the 'truth more likely to tell the truth in a second interview than children who did not participate in this procedure before questioning. Implications for the justice system are discussed.     

Fast gas chromatography of explosive compounds using a pulsed-discharge electron capture detector

The detection of a mixture of nine explosive compounds, including nitrate esters, nitroaromatics, and a nitramine in less than 140 sec is described. The new method employs a commercially available pulsed-discharge electron capture detector (PDECD) coupled with a microbore capillary gas chromatography (GC) column in a standard GC oven to achieve on-column detection limits between 5 and 72 fg for the nine explosives studied. The PDECD has the benefit that it uses a pulsed plasma to generate the standing electron current instead of a radioactive source. The fast separation time limits on-column degradation of the thermally labile compounds and decreases the peak widths, which results in larger peak intensities and a concomitant improvement in detection limits. The combination of short analysis time and low detection limits make this method a potential candidate for screening large numbers of samples that have been prepared using techniques such as liquid-liquid extraction or solid-phase microextraction.     

“从人到案” 破案模式的几个问题

从人到案的侦查破案模式,是指以犯罪嫌疑人为最初的工作对象,以人立案进行侦查的方式.目前,积极推广运用这种破案模式有十分重要的意义,而要充分运用该侦破模式则应具备以下条件建立与之相适应的刑侦体制及运行机制、建立完整科学的刑侦基础业务网络系统、努力开创出依靠群众的新路子.     

猪链球菌2型溶血素基因的检测及其序列分析

根据猪链球菌 2型的溶血素基因合成了一对可扩增长度为 14 96bp目的片段的引物 ,建立了检测溶血素基因的PCR方法。该方法对猪链球菌 2型参考株SS2 N株的检测结果为阳性 ,对马链球菌兽疫亚种 (C群 )参考株ATCC3 5 2 46、分离株SESZ Y、SESZ T、SESZ C和猪葡萄球菌、大肠埃希氏菌的检测结果均为阴性 ;用EcoRⅠ内切酶进行酶切 ,获得了与预期结果一致的 863bp和 63 3bp的 2个片段。经对SS2 1株的PCR产物进行测序及序列分析 ,表明其与 193 3株、P1/ 7株的核苷酸同源性分别为 99.7%和 10 0 %。     

The risk of detection

The clearance rate is often used as an indicator of the risk of detection, in spite of the fact that these are different matters. This article suggests a method to make estimates of the risk of detection based on information from the Swedish crime statistics. The risk of detection is expressed as a function of the dark figure. Empirical estimates of the risk are given for drunken driving, residential burglary, and assault between strangers. These estimates are followed up with some calculations concerning the impact of crime activity level on the risk of getting caught. One major conclusion of the findings is that the risk of detection varies very moderately with the dark figure. This means that if there is some knowledge of the dark figure, it is often possible to make fairly good estimates of the risk of detection.