Positional asphyxia: reflection on 2 cases

Positional asphyxia, a fatal condition arising because of the adoption of particular body positions, causing mechanical interference with pulmonary ventilation, can occur in various circumstances that are likely to come under the observation of the specialist in legal medicine (work, car accidents, torture, kidnapping, etc.). It is difficult to diagnose the cause of death in such cases because they generally present with an aspecific anatomopathologic picture. In some situations, positional asphyxia can be hard to distinguish from asphyxia because of chest compression. The main difference is in the way the event occurred: whether the particular position causing the asphyxia had been adopted by choice or by compulsion or necessity when an extrinsic mechanical action would result in traumatic asphyxia. The diagnosis of positional asphyxia is essentially based on 3 criteria: the body position must obstruct normal gas exchange, it must be impossible to move to another position, and other causes of natural or violent death must be excluded. To illustrate the main physiopathologic and diagnostic causes of positional asphyxia, the authors report 2 cases taken from the records of events that came under the observation of the Medico-Legal Sector of Bari University Hospital throughout the last 10 years.     

Population genetic data of eight tetrameric short tandem repeats (STRs) in Casablanca resident population to use in forensic casework

The allele frequencies for eight short tandem repeat (STR) loci HUMvWA, HUMFES/FPS, HUMF13A, HUMF13B, HUMTHO1, HUMTPOX, HUMCSF1P0, HUMLPL included in Geneprint STR kits were obtained from 234 unrelated individuals in Casablanca.     

Dental amalgam and mercury levels in autopsy tissues: food for thought

Eighteen cadavers from routine autopsy casework were subject to a study of tissue levels of total mercury in brain, thyroid, and kidney samples by atomic absorption. On these same cadavers, all dental amalgam fillings (the most important source of inorganic mercury exposure in the general population, according to the World Health Organization (WHO) were charted. Total mercury levels were significantly higher in subjects with a greater number of occlusal amalgam surfaces (>12) compared with those with fewer occlusal amalgams (0-3) in all types of tissue (all P < or = 0.04). Mercury levels were significantly higher in brain tissues compared with thyroid and kidney tissues in subjects with more than 12 occlusal amalgam fillings (all P < or = 0.01) but not in subjects with 3 or less occlusal amalgams (all P > or = 0.07).     

An evaluation of the Cozart RapiScan system as an on-site screening tool for drugs of abuse in a non-conventional biological matrix: vitreous humor

The aim of this project was to evaluate the Cozart RapiScan Oral fluid Drug Testing System as an on-site screening tool for vitreous humor samples collected during post-mortem examinations. Vitreous humor is easy to collect and as it is contained within the eye it is almost completely unaffected by post-mortem redistribution. The ability to carry out an initial drug screen on vitreous humor at the earliest stage of the death investigation process could contribute significantly to the assessment of the role drugs may have played prior to confirmation with toxicological analyses at the laboratory. Vitreous humor (n = 146) was collected from autopsy examinations (111 males and 35 females) with a specific focus on cases where death occurred following a road traffic accident or where an overdose was suspected. All samples were screened using the five-panel methadone Cozart RapiScan Cartridge with an overall positive rate of 29%. Of the positive results, 43% screened positive for benzodiazepines, 17% for cocaine, 7% for methadone and 33% for opiates. Positive samples, with the exception of benzodiazepines, and 20% of negative samples were analysed by GC/MS. This is the first reported use of this system as an on-site forensic tool in death investigation and for screening for drugs of abuse in vitreous humor. The conclusions from this study show that the Cozart RapiScan System could play an important role in obtaining information on the toxicological state of the person at the time of death.     

A comparison of efficiency of manual and automatic fibres search with the Maxcan fibre finder

The aim of this work was to study the efficiency of automatic fibre searching with the Maxcan fibre finder (Cox Analytical Systems, Sweden) in comparison to manual searching. The influence of some parameters (color, thickness, background noise) on the results of a fibre search was considered. Eighteen experimental tapes with different target fibres and different background noises were prepared in the laboratory. Searching of fibres was performed manually and with the Maxcan fibre finder by different operators from four European laboratories. Two laboratories have the Maxcan fibre finder system and the two instruments were used and compared in this study. The results show that searching with the Maxcan is generally as efficient as manual searching, except for very pale or very dark fibres. Note that the tapes used for these experiments were prepared in laboratory, and are not completely representative of the tape that could be obtained in real cases. To generalize the results obtained, further research on real case samples would be necessary.     

Correlation of Delta9-tetrahydrocannabinol concentrations determined by LC-MS-MS in oral fluid and plasma from impaired drivers and evaluation of the on-site Dräger DrugTest

Oral fluid (collected with the Intercept((R)) device) and plasma samples were obtained from 139 individuals suspected of driving under the influence of drugs and analyzed for Delta(9)-tetrahydrocannabinol (THC), the major psychoactive constituent of cannabis, using a validated quantitative LC-MS-MS method. The first aim of the study was to investigate the correlation between the analytical data obtained in the plasma and oral fluid samples, to evaluate the use of oral fluid as a 'predictor' of actual cannabis influence. The results of the study indicated a good accuracy when comparing THC detection in oral fluid and plasma (84.9-95.7% depending on the cut-off used for plasma analysis). ROC curve analysis was subsequently used to determine the optimal cut-off value for THC in oral fluid with plasma as reference sample, in order to 'predict' a positive plasma result for THC. When using the LOQ of the method for plasma (0.5 ng/mL), the optimal cut-off was 1.2 ng/mL THC in oral fluid (sensitivity, 94.7%; specificity, 92.0%). When using the legal cut-off in Belgium for driving under the influence in plasma (2 ng/mL), an optimal cut-off value of 5.2 ng/mL THC in oral fluid (sensitivity, 91.6%; specificity, 88.6%) was observed. In the second part of the study, the performance of the on-site Dr?ger DrugTest for the screening of THC in oral fluid during roadside controls was assessed by comparison with the corresponding LC-MS-MS results in plasma and oral fluid. Since the accuracy was always less than 66%, we do not recommend this Dr?ger DrugTest system for the on-site screening of THC in oral fluid.     

Validation of a large Italian Database of 15 STR loci

Results from a collaborative exercise with proficiency testing conducted by 20 Italian laboratories on the 15 loci included in the Identifiler kit were analyzed by allele sharing methods and by standard population genetics tests. The validated database, including about 1500 subjects, was merged with that of a previous exercise conducted on nine loci, and the resulting allele frequencies, subdivided by Italian region, were published on-line.     

Validation of an ELISA-based screening assay for the detection of amphetamine, MDMA and MDA in blood and oral fluid

The use of amphetamine and 'ecstasy' (MDMA) has increased exponentially in many European countries since the late nineties, leading to a rapid growth in the number of clinical and forensic analyses. Therefore, a rapid screening procedure for these substances in biological specimens has become an important part of routine toxicological analysis in forensic laboratories. The objective of this study was to evaluate the Cozart amphetamine enzyme-linked immunosorbent assay (ELISA) for the screening of plasma samples and oral fluid samples (collected with the Intercept device). Authentic plasma samples from drivers (n=360) were screened, using an 1:5-fold dilution. True positive, true negative, false positive and false negative results were determined relative to the in-house routine GC-MS analysis. Samples consisted of 144 amphetamine-only positives, 141MDMA/MDA-only positives, and 74 negatives when using the limit of quantitation as the cut-off level for confirmation (10 ng/mL). Using these results, receiver operating characteristic (ROC) curves were generated and optimal cut-off values for the screening assay were calculated. Analysis showed that the ELISA is able to predict the presence of either amphetamine or *MDMA/MDA (*MDMA as its metabolite MDA) in plasma samples with 98.3% sensitivity and 100% specificity at a cut-off value of 66.5 ng/mL d-amphetamine equivalents. A similar analysis was conducted on 216 oral fluid specimens collected from a controlled double blind study. Subjects received placebo or a high (100 mg) or low (75 mg) dose of MDMA. Oral fluid samples were collected at 1.5 and 5.5h after administration. Combined results of the analysis of the high and low dose oral fluid samples indicated a screening cut-off of 51 ng/mL d-amphetamine equivalents with both a sensitivity and specificity of 98.6% (using a LC-MS/MS confirmation cut-off of 10 ng/mL). In conclusion, these data indicate that the Cozart AMP EIA plates constitute a fast and accurate screening technique for the identification of amphetamine and MDMA/MDA positive plasma samples and oral fluid specimens (collected with Intercept. It should be emphasized that method validation should be performed for each type of biological matrix.     

Development of a pentaplex X-chromosomal short tandem repeat typing system and population genetic studies

Quadruplex and pentaplex systems for polymerase chain reaction amplification of X-chromosomal short tandem repeats DXS101, HPRTB, DXS8377, DXS981 (STRX1) and DXS6789 were developed for automated profiling of liquid and membrane-bound DNA samples. Chinese, Japanese and Thai populations were typed using a quadruplex system, while German and Philippine populations were analyzed using a five-locus system. Out of 88 meioses studied in Philippine family samples at each locus, a possible one repeat deletion (allele 51 to 50) at DXS8377 was observed in a father-daughter pair. Exact tests performed on genotype data from females in the Philippine, German and Thai populations indicated that these groups conform to Hardy-Weinberg equilibrium. Exact tests for population differentiation indicate significant variations in allele distributions, particularly at loci DXS101, DXS981 and DXS6789. Considered individually, DXS8377 was the most polymorphic and HPRTB the least polymorphic locus in these five populations. When the forensic efficiency of the quadruplex system was calculated, the combined power of discrimination among males (PD(M)) was no lower than 0.998, while among females the combined PD(F) was at least 0.9999 in all populations. The combined power of paternity exclusion was a minimum of 0.998 in trio cases and 0.98 in motherless cases. The addition of locus DXS6789 to the German and Philippine population databases using a pentaplex increased the forensic efficiency of the analysis system.