Neuropathological examination in forensic context

Different diseases of and trauma to the central nervous system (CNS), as well as their consequences are common causes of death and therefore it is important to examine the CNS appropriately in forensic autopsy, bearing in mind that the site of the disease is often as crucial as its nature. The CNS is a complex organ and its examination requires special methods and knowledge and often consultation with a neuropathologist. The prerequisite for the proper examination is correct handling and processing of the CNS. Because of its soft consistency fixation of the CNS in toto before detailed macroscopic analysis is recommended but guidance for an expedited limited examination is also given. The key features to which attention should be paid during the removal and later macroscopic examination of the CNS are described. Processing CNS for microscopy also requires special techniques and in addition to the routine stains both special histological and selected immunohistochemical stainings are often needed to reach the correct diagnosis.     

Routine Y-STR typing in forensic casework

In the field of molecular diagnosis, forensic casework analysis is one of the most demanding investigations, due to its social impact. Optimization of DNA typing multiplex reactions with identical cycling conditions as those required by autosomal short tandem repeats (STR) multiplex reduces errors, and saves time and reagents. Previously, we validated a five Y-STRs set, all of them generating single band patterns. This work reports the optimization of combined multiplexes, a triplex (DYS19, DYS390 and DYS391) and a duplex (DYS392 and DYS393), that can be amplified in identical cycling conditions as those required by commercially available multiplex autosomal STR kits. In addition both Y chromosome multiplexes can be combined for co-injection on a capillary electrophoresis based automated sequencer. Statistical attributes of the haplotypes of the five Y-STR investigated were evaluated in unrelated males from different metropolitan areas of Argentina. This system was successfully used for investigating more than 350 forensic routine cases in our country.     

The use of the likelihood ratio for evaluative and investigative purposes in comparative forensic handwriting examination

This paper extends previous research and discussion on the use of multivariate continuous data, which are about to become more prevalent in forensic science. As an illustrative example, attention is drawn here on the area of comparative handwriting examinations. Multivariate continuous data can be obtained in this field by analysing the contour shape of loop characters through Fourier analysis. This methodology, based on existing research in this area, allows one describe in detail the morphology of character contours throughout a set of variables. This paper uses data collected from female and male writers to conduct a comparative analysis of likelihood ratio based evidence assessment procedures in both, evaluative and investigative proceedings. While the use of likelihood ratios in the former situation is now rather well established (typically, in order to discriminate between propositions of authorship of a given individual versus another, unknown individual), focus on the investigative setting still remains rather beyond considerations in practice. This paper seeks to highlight that investigative settings, too, can represent an area of application for which the likelihood ratio can offer a logical support. As an example, the inference of gender of the writer of an incriminated handwritten text is forwarded, analysed and discussed in this paper. The more general viewpoint according to which likelihood ratio analyses can be helpful for investigative proceedings is supported here through various simulations. These offer a characterisation of the robustness of the proposed likelihood ratio methodology.     

Application of direct PCR in forensic casework

Direct PCR is fast becoming a popular method in forensic science due to the advantages of saving time and money in the lab while increasing the probability of obtaining substantial results has a positive rippling effect. A laboratory is able to reduce the time spent on processing trace DNA samples, which can lead to investigators receiving important information in a timely manner that may not have been possible using standard methods. This study highlights the benefits of direct PCR in forensic casework by analysing trace and touch DNA on a range of substrates and exploring the loss of initial DNA due to extraction.     

The evidential value of cosmetic foundation smears in forensic casework

Cosmetic foundation products are easily transferred to clothing and other surfaces as a result of contact with such objects. Examination of past cases involving cosmetics in New Zealand has shown cosmetic foundation to be one of the more common cosmetic products encountered. The aim of this research was to determine the most discriminating method for the comparison of transferred foundation with samples obtained from a known source in forensic casework. Fifty-three foundation samples were analyzed by Fourier transform infrared spectroscopy (FTIR), gas chromatography with a flame ionization detector (GC-FID) and scanning electron microscopy-energy dispersive X-Ray analysis (SEM-EDX). It was found that a 5 mm2 section of a light smearing was enough to provide detectable results. The discriminating powers for FTIR, SEM-EDX and GC-FID were 98.3, 93.8, and 82.0% respectively. A combination of all three techniques provided a discriminating power of 99.7%, meaning that almost complete discrimination was achieved between the foundation samples.     

Application of mtDNA SNP analysis in forensic casework

In this study six forensic cases are presented where the routine analysis of samples for short tandem repeats (STRs) failed. The sequencing of the mitochondrial hypervariable region I (HVR I) also failed. Nevertheless, it was possible to analyse the samples with mitochondrial DNA (mtDNA) single nucleotide polymorphisms (SNPs) via SNaPshot technique. The age of the analysed samples ranged from 2 months to 1400 years. Saliva-, blood-, sperm-, hair-, tooth- and bone-samples were investigated. Furthermore the mtDNA SNP analysis of a forensic case sample showing a mixed stain profile is presented. It was possible to discriminate two different haplogroups in this mixed-person stain. If compared to another mtDNA SNP profile that was found in a hair, the discriminating SNPs of the hair were as well found in the mixed-person stain.To disburden the SNP analysis in forensic casework, haplogroup assignment criteria and quality criteria for mtDNA SNaPshot analysis are announced.     

Use of Bayesian networks in forensic soil casework

Forensic soil comparisons can be of high evidential value in a forensic case, but become complex when multiple methods and factors are considered. Bayesian networks are well suited to support forensic practitioners in complex casework. This study discusses the structure of a Bayesian network, elaborates on the in- and output data and evaluates two examples, one using source level propositions and one using activity level propositions. These examples can be applied as a template to construct a case specific network and can be used to assess sensitivity of the target output to different factors and identify avenues for research.     

Analysis of condom lubricants for forensic casework

The detection of DNA is inhibited in cases of sexual assault involving condom use. Trace evidence, including condom lubricant residues, provides crucial associative evidence in such cases. The existing Fourier transform infrared spectroscopy (FTIR) methods for lubricant analysis and detection are limited with regard to sensitivity and discrimination. The aim of this research was to establish a new method as an alternative to FTIR for the analysis of condom lubricant residues. Pyrolysis gas chromatography-mass spectrometry (PyGC-MS) and GC-MS are highly sensitive methods of analysis for a wide range of chemical substances. PyGC-MS and GC-MS were used to analyze condom lubricants in standard solution, from clean swabs and from postcoital swabs. Pyrolysis of polydimethylsiloxane (PDMS) lubricant forms cyclic products known as cyclic dimethyl siloxanes (DMS), which are separated and detected by the GC-MS. The polyethylene glycol (PEG) lubricant can be analyzed by GC-MS directly from solution. The methods of extraction and analysis presented in this paper were shown to be significantly more sensitive than FTIR for the analysis of PDMS and PEG condom lubricants. PDMS was detected as low as 1 mug in standard solution and from clean swabs using the PyGC-MS method. PEG was detected as low as 0.5 microg from standard solution and 50 mug from clean swabs using the GC-MS method. Unfortunately, we were unable to provide further discrimination between condom brands and subbrands. The methods established throughout the research were used successfully to detect condom lubricants from donated postcoital swabs. Lubricants were detected in abundance on swabs 12 h postcoitus. Recommendations are made regarding implementation of new methods for routine analysis of casework samples along with strict pyrolysis interpretation criteria to minimize the possibility of misinterpretation of false positives.     

Quantifiler observations of relevance to forensic casework

The Quantifiler (QF) kit is regularly used by forensic scientists for DNA quantitation. We performed in-house validation studies which revealed some interesting observations. The QF standard displayed a two-fold difference between two different lot numbers which suggests that every standard should be tested prior to use. The Promega K562 DNA standard works well with the QF kit. c. 41% of samples that inhibited the internal PCR control (IPC) system within the QF kit still produced good Profiler Plus reactions. QIAquick was effective at removing inhibitors. The presence of dyes within casework samples were observed not to inhibit QF amplifications. Template DNA greater than 100 ng/muL appeared to inhibit the IPC. Close to identical concentration results were obtained when alternative analysis settings were used. These validation findings will assist DNA processes involved in forensic casework.     

Use of subpopulation data in Australian forensic DNA casework

DNA profiling evidence presented in court should be accompanied by a reliable estimate of its evidential weight. In calculating such statistics, allele frequencies from commonly employed autosomal microsatellite loci are required. These allele frequencies should be collected at a level that appropriately represents the genetic diversity that exists in the population. Typically this occurs at broadly defined bio-geographic categories, such as Caucasian or Asian. Datasets are commonly administered at the jurisdictional level. This paper focuses on Australian jurisdictions and assesses whether this current practice is appropriate for Aboriginal Australian and Caucasian populations alike. In keeping with other studies we observe negligible differences between Caucasian populations within Australia when segregated geographically. However segregation of Aboriginal Australian population data along contemporary State and Territory lines appears to mask the diversity that exists within this subpopulation. For this reason datasets collated along more traditional lines may be more appropriate, particularly to distinguish the most genetically differentiated populations residing in the north of the continent.     

Twenty-seven years of forensic anthropology casework in New Mexico

A review of anthropological consult cases for the New Mexico Office of the Medical Investigator was conducted for the years 1974 through 2000. A total of 596 cases are summarized and information is presented on the sex and age of the individuals, season of recovery, depositional environment, body covering, time since death, perimortem trauma, postmortem animal activity, and skeletal element recovery. Results reveal a higher percentage of male victims (76%). No variation is seen in the seasonal distribution of cases. In cases with known time since death, 35% were recovered within one week while 30% had a postmortem interval exceeding one year. Depositional environments include surface (45%), burial (13%), and airplane crashes (9.5%). In 42% of the cases, no evidence of perimortem trauma was observed. Postmortem animal activity was noted in 46% of cases. Data presented in this study may prove useful in supporting expert witness testimony and generating future research models.     

Applicability of DNA analysis on adhesive tape in forensic casework

Adhesive tape is commonly used in crimes and is often the subject of forensic evaluation. DNA analysis of adhesive tape can provide DNA profiles of suspects. The object of this study was to evaluate the applicability of DNA analysis on adhesive tape samples in forensic casework. We retrospectively reviewed all cases involving adhesive tape or similar items received by our institute for DNA analysis during the past 11 years. From 100 forensic cases reviewed, 150 adhesive tape samples were examined. A total of 98 DNA profiles were obtained from these samples. Sixty-two of the profiles provided feasible case-relevant information. In conclusion, DNA profiling of adhesive tape samples can be useful in a variety of forensic cases.     

The forensic entomologist in the context of the forensic pathologist's role.

An adequate death investigation requires the combined efforts and cooperation of experts in different disciplines: crime scene technicians, death investigators, forensic pathologists, anthropologists, entomologists, other medical and non-medical professionals. These front-line experts play a crucial role in every death investigation process. The forensic pathologist normally has the legal authority to take charge of the dead body at a death scene and his primary functions are the exterior and interior examination of the cadaver by analyzing the extent of antemortem injuries and the postmortem changes and the recovery of physical evidence. He is responsible for determining how, when and why of any death which is the result of violence, suspicious or unexplained circumstances or a death which is sudden or unattended, defending and explaining the reasons for making these diagnoses in a courtroom. The forensic entomologist can provide invaluable aid in death cases where human remains are colonized by insects and in the overall investigation. His principal role is to identify the arthropods associated with such cases and to analyze entomological data for interpreting insect evidence. He is responsible for determining the period of insect activity according to all the variables affecting insect invasion of remains and their development. The major goal of medico-criminal entomology is to contribute to the determination of the time, cause, manner and place of the investigated death (especially on badly decomposed corpses or skeletonized human remains) with the support of all the elements which can be inferred from the study of insects found on the cadaver or nearby. The application of techniques devised recently in forensic entomology can allow experts in the field to collect strong entomological evidence and provide useful information not only in a death investigation including movement or storage of the remains following death, time of dismemberment, postmortem artifacts on the body but also at the scene, and even more in child neglect, sexual molestation and identification of suspects. As the role of the forensic entomologist at the death scene, at the autopsy and in the laboratory is defined and well known, this paper focuses on the difficulties that could arise if forensic pathologists and entomologists are uncertain about the procedures that they have to follow, do not realize the value of objective findings or fail to evaluate them. Although every forensic case presents a slightly different set of circumstances and has to be tackled individually, the forensic pathologist should work with the forensic entomologist from the visual observations of the cadaver on the scene, through the collection of arthropods and temperature data at the death scene and at the autopsy, up to the final report with the interpretation of entomological and other biological evidence.     

7个Y-STR基因座单倍型及其法医学应用

目的调查7个Y-STR基因座单倍型及其法医学应用。方法利用二组复合扩增体系,(Ⅰ:DYS391、GATA-A4、GATA-A10和GATA-H4;Ⅱ:DYS439、DYS437和DYS434)检测7个Y染色体特异性的STR基因座,并用聚丙烯酰胺凝胶电泳和银染显色技术进行基因分型。结果在广东汉族372名无关男性个体中,二组7个基因座分别检出5、7、6、5和6、4、4个等位基因,共检出254种单倍型,其中201种为唯一的。单倍型基因多样性为0.9960。结论7个Y-STR基因座具有很高的识别能力,对建立Y染色体STR数据库,研究群体遗传学和进行法医学鉴定有重要意义。     

A simple automated instrument for DNA extraction in forensic casework

The Qiagen BioRobot EZ1 is a small, rapid, and reliable automated DNA extraction instrument capable of extracting DNA from up to six samples in as few as 20 min using magnetic bead technology. The San Diego Police Department Crime Laboratory has validated the BioRobot EZ1 for the DNA extraction of evidence and reference samples in forensic casework. The BioRobot EZ1 was evaluated for use on a variety of different evidence sample types including blood, saliva, and semen evidence. The performance of the BioRobot EZ1 with regard to DNA recovery and potential cross-contamination was also assessed. DNA yields obtained with the BioRobot EZ1 were comparable to those from organic extraction. The BioRobot EZ1 was effective at removing PCR inhibitors, which often co-purify with DNA in organic extractions. The incorporation of the BioRobot EZ1 into forensic casework has streamlined the DNA analysis process by reducing the need for labor-intensive phenol-chloroform extractions.     

Cognitive forensics and experimental research about bias in forensic casework

Understanding and coping with cognitive bias in forensic science requires multiple studies, utilizing both laboratory-based experiments and data from casework. Neither type of studies has ever been conducted to examine bias in mixture DNA interpretations. A study that includes both types of data has recently been published in Science and Justice. The data and statistical analysis clearly — at the very least — suggest that bias may potentially influence DNA mixture interpretation. This is due, in part, to the subjective elements in interpretation of mixture DNA. The issue of bias and other cognitive influences is of a sensitive nature and presents complex experimental challenges. Our study takes a step in examining these issues and calls for more research.     

Experimental and casework validation of ambient temperature corrections in forensic entomology

This paper expands on Archer (J Forensic Sci 49, 2004, 553), examining additional factors affecting ambient temperature correction of weather station data in forensic entomology. Sixteen hypothetical body discovery sites (BDSs) in Victoria and New South Wales (Australia), both in autumn and in summer, were compared to test whether the accuracy of correlation was affected by (i) length of correlation period; (ii) distance between BDS and weather station; and (iii) periodicity of ambient temperature measurements. The accuracy of correlations in data sets from real Victorian and NSW forensic entomology cases was also examined. Correlations increased weather data accuracy in all experiments, but significant differences in accuracy were found only between periodicity treatments. We found that a >5°C difference between average values of body in situ and correlation period weather station data was predictive of correlations that decreased the accuracy of ambient temperatures estimated using correlation. Practitioners should inspect their weather data sets for such differences.     

DNA mixtures in forensic casework: a 4-year retrospective study

Occasionally interpretation guidelines from validation studies are difficult to apply to real forensic casework, especially in the case of mixed samples. Exogenous contamination, an unknown number of contributors or unbalanced proportion of each one in the sample and a varied degree of degradation of the biological materials, contribute to the difficulties in the interpretation of sample profiles. In this paper we have reviewed all the mixed genetic STR profiles encountered in our laboratory over 4 years (1997-2000) and evaluated the problems in the interpretation of the results. From 1547 criminal cases with 2424 samples typed, 163 showed a mixed profile (6.7%). We have observed that occasionally, a mixture appeared in the same sample with one multiplex amplification kit (e.g. Blue) and not with another (e.g. Green). From our results, it can be suggested that technical characteristics of the different fluorochrome groups in the multiplexes override the molecular characteristics of each STR in their capacity to detect mixtures.     

Validation of the AMPFlSTR SGM plus system for use in forensic casework

The AMPFlSTR((R)) SGM Plus system is a commercially available STR multiplex produced by Applied Biosystems, a division of Perkin Elmer, Foster City, California, USA that supersedes SGM. The multiplex contains the six SGM loci, amelogenin and four additional loci. These additional loci are D3S1358, D19S433, D16S539 and D2S1338. Consequently, the match probability is significantly improved (conservatively quoted as 1 in 10(9) for reporting a full profile match). The system was subjected to validation. For example, ageing and degradation studies demonstrated semen stains to be the most stable evidence type, whereas buccal scrapes were the least stable. An apparent rise in the sensitivity increases the chance of obtaining successful results from the more difficult samples submitted for analysis. Two of the new loci (D3S1358 and D19S433) are low molecular weight (between 100 and 150 base pairs); this improved the success rates of the degraded samples where high molecular weight loci may drop out. Of 26 non-primates tested, four gave results that appeared as single peaks and were unlikely to cause interpretation problems. None of the 19 micro-organisms tested gave discernible results. Extensive casework and simulated casework studies demonstrated that SGM and SGM plus results were comparable. There was one example of a null allele (primer binding site mutation) recorded at the HUMFIBRA locus (in both systems). However, a concordance study of 1000 samples using both SGM and SGM plus did not demonstrate any differences in typing.