Person identification by gait analysis and photogrammetry

Surveillance images from a bank robbery were analyzed and compared with images of a suspect. Based on general bodily features, gait and anthropometric measurements, we were able to conclude that one of the perpetrators showed strong resemblance to the suspect. Both exhibited a gait characterized by hyperextension of the leg joints, and bodily measurements did not differ by more than 6 mm on average. The latter was quantified by photogrammetry: i.e., measuring by using images of the perpetrator as captured by surveillance cameras. Using the computer software Photomodeler Pro, synchronous images from different cameras were compared and concurrent body features were identified. The program could then render the perpetrator as a three dimensional, high-precision, scalable and measurable object.     

A medical model for criminalistics education

The history of medical education during the period of 1870 to 1926 is examined in the context of current issues confronting education in the forensic laboratory sciences. Medical education was radically altered during this period, changing from a rudimentary lecture/apprenticeship system into its modern form. Although the motivating forces had developed over some time, the actual change was quite rapid. By examining how this change occurred, we gain insight into how changes in our own profession might be initiated. Parallels between our current situation and that in medical education 117 years ago include: (1) the primary burden of professional education is borne outside the university in an apprenticeship system, (2) the apprenticeship system is overburdened by a dramatic expansion in the knowledge and skills needed for professional practice, (3) there is no standardized curriculum or accreditation process for educational programs, and (4) there is no educational program that incorporates formal clinical education. Based on this historical analysis, three major goals are proposed: (1) active entreprenurial promotion of professional educational programs by academics, (2) creation of a committee within the American Academy of Forensic Sciences to critique and rate university programs, and (3) the development of a well-defined clinical education program. A model for formalized clinical education in the forensic laboratory sciences is proposed, incorporating clinical professors, student clerkships, and university control over instruction within an operational forensic science laboratory. Benefits from this arrangement include: efficient combination of physical plants, added personnel resources in the laboratory, rapid introduction of research into the laboratory, enhanced prestige for both academics and practitioners, and relief of the laboratory's in-house training burden.     

人体组织/体液来源的法医学鉴定

生物检材的组织/体液来源鉴定是法医学检验的重要内容之一。法医学组织/体液鉴定的方法较多,无论是基于酶促反应或免疫学检测的传统鉴定方法,还是光谱法或近年来基于mRNA、microRNA或DNA甲基化差异的分子生物学组织鉴定技术,均各有特点。本文就各种法医学组织/体液鉴定方法的特点及其法医学应用价值作一简要综述。     

The identification of individuals by observational gait analysis using closed circuit television footage

This study investigated the ability of individuals with experience in gait analysis to identify people by observing features of gait recorded by closed circuit television cameras (CCTV). Seven experienced analysts each viewed five samples of footage. Each sample showed a “target walker” and five “suspect walkers.” The task of the experienced analysts was to determine which, if any, of the “suspect walkers” was the “target walker.” All of the participant “walkers” wore identical loose fitting clothing to mask anatomical and body contour features, and balaclavas to obscure facial features. The overall results showed that the experienced analysts made a correct decision in 124 of 175 cases (71%), significantly better than would have been expected to have occurred by chance (p < 0.05). A significant variation in correct decisions (p < 0.05) was shown to occur between the various angles from which the footage was recorded, footage recorded in the saggital plane showing the highest number of correct decisions. Significantly more correct decisions (p < 0.05) were also shown to occur when the footage of the “target walker” and that of the “suspect walker” were taken from the same angle. The results suggest that individuals with experience in gait analysis perform well in the comparative identification of suspects from CCTV footage, and therefore do have a role to play as expert witnesses in this field.     

Validation of a 21-locus autosomal SNP multiplex for forensic identification purposes

A single nucleotide polymorphism (SNP) multiplex has been developed to analyse highly degraded and low copy number (LCN) DNA template, i.e. <100 pg, for scenarios including mass disaster identification. The multiplex consists of 20 autosomal non-coding loci plus Amelogenin for sex determination, amplified in a single tube PCR reaction and visualised on the Applied Biosystems 3100 capillary electrophoresis (CE) system. Allele-specific primers tailed with shared universal tag sequences were designed to speed multiplex design and balance the amplification efficiencies of all loci through the use of a single reverse and two differentially labelled allele denoting forward universal primers. As the multiplex is intended for use with samples too degraded for conventional profiling, a computer program was specifically developed to aid interpretation. Critical factors taken into account by the software include empirically determined extremes of heterozygous imbalance (Hb) and the drop-out threshold (Ht) defined as the maximum peak height of a surviving heterozygous allele, where its partner may have dropped out. The discrimination power of the system is estimated at 1 in 4.5 million, using a White Caucasian population database. Comparisons using artificially degraded samples profiled with both the SNP multiplex and AMPFISTR SGM plus (Applied Biosystems) demonstrated a greater likelihood of obtaining a profile using SNPs for certain sample types. Saliva stains degraded for 147 days generated an 81% complete SNP profile whilst short tandem repeats (STRs) were only 18% complete; similarly blood degraded for 243 days produced full SNP profiles but only 9% with STRs. Reproducibility studies showed concordance between SNP profiles for different sample types, such as blood, saliva, semen and hairs, for the same individual, both within and between different DNA extracts.     

The effectiveness of various strategies to improve DNA analysis of formaldehyde-damaged tissues from embalmed cadavers for human identification purposes

Formalin-fixed tissues provide the medical and forensic communities with alternative and often last resort sources of DNA for identification or diagnostic purposes. The DNA in these samples can be highly degraded and chemically damaged, making downstream genotyping using short tandem repeats (STRs) challenging. Therefore, the use of alternative genetic markers, methods that pre-amplify the low amount of good quality DNA present, or methods that repair the damaged DNA template may provide more probative genetic information. This study investigated whether whole genome amplification (WGA) and DNA repair could improve STR typing of formaldehyde-damaged (FD) tissues from embalmed cadavers. Additionally, comparative genotyping success using bi-allelic markers, including INDELs and SNPs, was explored. Calculated random match probabilities (RMPs) using traditional STRs, INDEL markers, and two next generation sequencing (NGS) panels were compared across all samples. Overall, results showed that neither WGA nor DNA repair substantially improved STR success rates from formalin-fixed tissue samples. However, when DNA from FD samples was genotyped using INDEL and SNP-based panels, the RMP of each sample was markedly lower than the RMPs calculated from partial STR profiles. Therefore, the results of this study suggest that rather than attempting to improve the quantity and quality of severely damaged and degraded DNA prior to STR typing, a more productive approach may be to target smaller amplicons to provide more discriminatory DNA identifications. Furthermore, an NGS panel with less loci may yield better results when examining FD samples, due to more optimized chemistries that result in greater allelic balance and amplicon coverage.     

The analysis of illicit methaqualone containing preparations by gas chromatography-mass spectrometry for forensic purposes

A validated gas chromatographic-mass spectrometric method for quantitative analysis of methaqualone (MTQ) in illicit preparations is reported. The method proved to have a coefficient of variation of below 5%. Four batches of seized tablets, two pairs with similar imprints, were analyzed. It was found that the average MTQ concentration in all four batches of tablets differed significantly (p = 0.01) rendering it impossible to conclude that, on the basis of MTQ concentration alone, the batches with a similar logo originated from the same manufacturer or manufacturing batch. Conversely, it can be said that in this case, the four batches originated from either different clandestine laboratories or manufacturing batches.     

Elemental analysis of soil samples for forensic purposes by inductively coupled plasma spectrometry--precision considerations

Major and trace elemental composition provides a powerful basis for forensic comparison of soils, sediments and rocks. However, it is important that the potential 'errors' associated with the procedures are fully understood and quantified, and that standard protocols are applied for sample preparation and analysis. This paper describes such a standard procedure and reports results both for instrumental measurement precision (repeatability) and overall 'method' precision (reproducibility). Results obtained both for certified reference materials and example soils show that the instrumental measurement precision (defined by the coefficient of variation, CV) for most elements is better than 2-3%. When different solutions were prepared from the same sample powder, and from different sub-sample powders prepared from the same parent sample, the CV increased to c. 5-6% for many elements. The largest variation was found in results for certified reference materials generated from 23 instrument runs over an 18 month period (mean CV=c. 11%). Some elements were more variable than others. W was found to be the most variable and the elements V, Cr, Co, Cu, Ni and Pb also showed higher than average variability. SiO2, CaO, Al2O3 and Fe2O3, Rb, Sr, La, Ce, Nd and Sm generally showed lower than average variability, and therefore provided the most reliable basis for inter-sample comparison. It is recommended that, whenever possible, samples relating to the same investigation should be analysed in the same sample run, or at least sequential runs.     

广州话语音声纹鉴定中的量化分析研究

本研究从一般元音(音节核心)的同一认定方法着手,着重从定量分析方面研究声学特征参量,把多元统计方法使用到声纹鉴定中。通过计算变异系数、相关系数、正态性检验、方差分析等基本统计分析,对于男性语音,制定了马氏距离判别数学模型,判对率达98.3%;对于女性语音,制定了费歇(Fisher)判别数学模型,判对率达93.5%。本研究解决了声纹鉴定对声学特征参量定量分析方面的问题,确定了判定阈值及鉴定所需音节数,提供了一种新的语音判别方法。     

The use of medical examinations for employment purposes

This article examines a number of legal issues which arise where medical examinations or tests are used in the employment context, either to test the suitability of a prospective employee in pre-employment situations or to ascertain the fitness of existing employees. Employer justifications for seeking medical information usually relate to attempts to comply with health and safety legislation and to reduce workers compensation costs. This article discusses the legal obligations involved in pre-employment medical testing and, in particular, employee obligations to provide correct information in relation to their health to a prospective employer. It also notes the consequences for employees of providing false information in relation to workers compensation claims and dismissal cases. The article notes the growing trend of requiring drug and alcohol testing for existing employees, particularly in the mining industry. The article concludes by noting that employers need to take care in seeking medical information, and that it should not simply be done as a mechanical, matter-of-course exercise. Failure to observe anti-discrimination laws may result in the employer facing allegations of misuse of medical information and claims for damages for discrimination.     

Headspace profiling of cocaine samples for intelligence purposes

A method for determination of residual solvents in illicit hydrochloride cocaine samples using static headspace-gas chromatography (HS-GC) associated with a storage computerized procedure is described for the profiling and comparison of seizures. The system involves a gas chromatographic separation of 18 occluded solvents followed by fully automatic data analysis and transfer to a PHP/MySQL database. First, a fractional factorial design was used to evaluate the main effects of some critical method parameters (salt choice, vial agitation intensity, oven temperature, pressurization and loop equilibration) on the results with a minimum of experiments. The method was then validated for tactical intelligence purposes (batch comparison) via several studies: selection of solvents and mathematical comparison tool, reproducibility and "cutting" influence studies. The decision threshold to determine the similarity of two samples was set and false positives and negatives evaluated. Finally, application of the method to distinguish geographical origins is discussed.