Can computer forensic tools be trusted in digital investigations?

This paper investigates whether computer forensic tools (CFTs) can extract complete and credible digital evidence from digital crime scenes in the presence of file system anti-forensic (AF) attacks. The study uses a well-established six stage forensic tool testing methodology based on black-box testing principles to carry out experiments that evaluate four leading CFTs for their potential to combat eleven different file system AF attacks. Results suggest that only a few AF attacks are identified by all the evaluated CFTs, while as most of the attacks considered by the study go unnoticed. These AF attacks exploit basic file system features, can be executed using simple tools, and even attack CFTs to accomplish their task. These results imply that evidences collected by CFTs in digital investigations are not complete and credible in the presence of AF attacks. The study suggests that practitioners and academicians should not absolutely rely on CFTs for evidence extraction from a digital crime scene, highlights the implications of doing so, and makes many recommendations in this regard. The study also points towards immediate and aggressive research efforts that are required in the area of computer forensics to address the pitfalls of CFTs.     

常染色体STR突变基因座父权指数计算

目的概括归纳常染色体STR突变基因座的父权指数计算方法,以在实际检案中应用推广。方法根据目前对常染色体STR基因座突变的认识,用经验递减模型从基因座突变率计算等位基因突变率,分别推导在标准三联体和二联体亲子鉴定中STR突变基因座的父权指数计算式,并举例进行演算。结果总结了在标准三联体鉴定中,只允许假设父突变和既允许假设父也允许母发生突变时,以及二联体鉴定时X和Y的计算式。结论STR基因座发生突变时计算得的父权指数明显低于未发生突变时,提示要检测更多的遗传标记才能使累积父权指数达到认定亲权关系的标准。     

A report of the 2002–2008 paternity testing workshops of the English speaking working group of the International Society for Forensic Genetics

The English Speaking Working Group (ESWG) of the International Society for Forensic Genetics (ISFG) offers an annual Paternity Testing Workshop open to all members of the group. Blood samples, a questionnaire and a paper challenge are sent to the participants. Here, we present the results of the 2002–2008 Paternity Testing Workshops with the objective to evaluate the uniformity of DNA-profiling and conclusions of the participating laboratories as well as to clarify tendencies in typing strategies and biostatistical evaluations of the laboratories. The numbers of participating laboratories increased from 46 in 2002 to 68 in 2008. The results showed an increasing degree of concordance concerning methods and DNA systems used and a high degree of uniformity in typing results with discrepancies in 0.1 and 0.3 % of all submitted PCR-based results. The paper challenges showed uniformity in the calculation of the weight of evidence for simple cases with straight-forward genetic constellations. However, a high degree of variation existed in complex scenarios with rare genetic constellations such as genetic inconsistencies/possible silent alleles, rare alleles and haplotypes.     

Mutation rates at 14 STR loci in the population from Pernambuco, Northeast Brazil

Definition about mutation rates of short tandem repeats (STRs) loci used in forensic analysis are useful for the correct interpretation of resulting genetic profiles and the definition of criterions for exclusion in paternity testing. Germline mutation of 14 STR loci was studied for 54,105 parent–child allelic transfers from 2575 paternity testing cases carried out during 2000–2007 from the Pernambuco State, Northeast Brazil. The parenthood in each of these cases was highly validated (probability > 99.99%). We identified 43 mutations at 12 loci. Locus-specific mutation rate estimates varied between 2 × 10⁻⁴ and 2 × 10⁻³, and the overall mutation rate estimate was 8 × 10⁻⁴. Mutation events in the male germline were more frequent than in the female germline. The majority of the mutations could be explained by losses or gains of one repeat unit and there was no evidence for selection between insertion or deletion changes. Our data were compared with those of Portuguese and North-American populations for CSF1PO, D18S51, D21S11, D7S820, TH01, TPOX and demonstrated, despite the great difference in the size of the sample, that mutation rates of STR loci in a mixed population do not differ from that encountered in different populations.     

ABO genotyping by duplex amplification and oligonucleotide arrays assay

Objective

Research on the application feasibility of ABO genotyping for forensic identification by oligonucleotide arrays assay.

Methods

Oligonucleotide microarrays which detect three different SNPs in exon 6 and exon 7 for ABO genotyping were used. After hybridization wash, the arrays were scanned and fluorescence intensities were analyzed using microarray population studies on ABO was carried out in a sample of 115 unrelated Chinese Han individuals oligonucleotide arrays for genotype detection. The method was also applied to cases.

Results

Technique could identify six genotypes of ABO system and the results of GeneChip analyses confirmed by PCR–RFLP. According to the results of population studies, no significant deviations Hardy–Weinberg equilibrium could be found. The observed heterozygosity (H-obs) was 0.591. Expected heterozygosity (H-exp) was 0.616. The polymorphic information content (PIC) was the average exclusion probability in paternity testing for duos (PE (1)) was 0.188. The average exclusion probability in paternity testing for trios (PE(2)) was 0.344. The discrimination power 0.777.

Conclusion

The data and case application demonstrated that ABO typing by oligonucleotide probe arrays was a useful technique for paternity testing and individual identification.     

从亲子鉴定的问题看标准化规范化管理的重要性

近年来,亲子鉴定技术在我国发展较快,越来越多的人应用这一鉴定手段维护了自己的合法权益.但我们发现,我国目前对鉴定部门的管理却相对滞后,主要表现为实验室缺乏规范化管理、鉴定机构良莠不齐、技术标准不够完备以及缺乏实验室的质量检测体系等.这些问题如不解决,将不适应司法体制改革的趋势,阻碍鉴定技术科学、公正地为司法实践服务.因此,我们呼吁有关部门对这一问题加以重视、加强协作,使科学鉴定早日走上标准化、规范化管理的道路.     

Evaluation and applicability of Alere iCup DX 14 for rapid postmortem urine drug screening at autopsy

Performing point‐of‐care urine drug screen testing at autopsy by a forensic pathologist may provide an early indication of the presence of analytes of interest during autopsy. An evaluation for the screening of 14 classes of common drugs of abuse in postmortem urine by the point‐of‐care screening device, Alere iCup DX 14, is presented. One hundred ninety postmortem urine samples were screened with the iCup occurring at autopsy by the forensic pathologist. Positive and negative results obtained from the screening kit were evaluated against confirmatory test results obtained using routine forensic toxicology analyses that employed LC‐MS/MS and GC‐MS to detect a combination of over 85 common drugs of abuse and medications. Sensitivity for each respective iCup drug class ranged from 66% (buprenorphine) to 100% (methadone, tricyclic antidepressants). Specificity for each respective iCup drug class ranged from 89% (benzodiazepines) to 100% (amphetamines, barbiturates, buprenorphine, 3,4‐methylenedioxymethamphetamine, methadone). Positive predictive values ranged from 44% (benzodiazepines) to 100% (amphetamines, barbiturates, buprenorphine, methylenedioxymethamphetamine, methadone), while negative predictive values ranged from 96% (methamphetamine) to 100% (barbiturates, methadone, tricyclic antidepressants). A high false‐positive rate was yielded by the benzodiazepine class. The lack of fentanyl screening in the point‐of‐care device is a significant limitation considering its prolific prevalence in forensic casework. The results obtained in the study should be acknowledged when considering the use of the Alere iCup DX 14 in the context of postmortem casework to help indicate potential drug use contemporaneously with autopsy and when requiring such preliminary results prior to the release of a final forensic toxicology report.     

物证检验技术在查处交通肇事案中的作用

物证检验技术在查处交通肇事案件中具有重要作用 :1、对车辆痕迹进行直观分析、测量比对 ,发现事实 ,确定事故责任 ,迅速解决纠纷 ;2、运用仪器分析技术 ,为查找逃逸车辆 ,认定肇事车辆、确定责任人提供科学依据 ;3、结合痕迹学原理 ,可重现案发的情况 ,为分析事故成因提供依据 ;4、充分运用物证检验技术识破伪装案件 ,去伪存真 ,正确认定案件性质 ,有效打击犯罪     

外伤后阴茎勃起功能障碍的夜间阴茎勃起功能监测

目的 夜间阴茎勃起功能监测(NPT)技术在阴茎勃起功能障碍程度鉴定中的法医学意义。方法 用RIGISCAN PLIJS SYSTEM,对13例外伤后主诉阴茎勃起障碍的被鉴定人进行监测。结果 NPT检查的13例被鉴定人,阴茎勃起功能正常者3例,轻度减退者5例,中度减退者2例,完全丧失者3例。其中在IIEF、自我勃起功能评价为严重功能障碍的5例中,NPT检查正常者1例,轻度减退者1例,中度减退者1例,完全丧失者2例。结论　NPT技术能够有效的确定阴茎勃起功能障碍的程度,为法医学损伤程度鉴定或伤残程度评定提供依据。     

Legal issues in oral fluid testing

The use of oral fluid for drugs of abuse testing has received increased attention with the availability of accurate methods for the collection and analysis of drugs in oral fluid specimens. Already used in the transportation and insurance industries, there is increasing interest in oral fluid drug testing in the workplace, schools, roadside driving under the influence of drugs, and criminal justice. Given that sanctions may accrue from positive test results, legal challenges are to be expected. However, with its established scientific base, demonstrated accuracy and reliability of collection and test methods, and current positive regulatory developments, it seems clear that the use of oral fluid as a specimen for drugs of abuse testing will be able to withstand judicial scrutiny.