The statistical variability of blood alcohol concentration measurements in drink-driving cases

Like many other places in the world, Hong Kong has drink-driving legislation which prohibits a driver from having in his blood alcohol exceeding a prescribed limit while in control of a motor vehicle. The accuracy of measuring this alcohol concentration is obviously of prime concern as an erroneous result can avert the administration of justice. The common practice is to deduct all errors from the measured value and compare the deducted value with the prescribed limit, so that the benefit of all errors of the measurement is given to the driver. It is therefore important for any laboratory responsible for measuring blood alcohol concentrations to identify and quantify all errors associated with the measurement. The present study examined 900 blood alcohol determinations carried out by the Hong Kong Government Laboratory (HKGL) on cases of suspected drink driving. The determinations were performed by 5 different analysts with two different sets of instruments during 1995-1997. Statistical analysis indicated that the instruments had no bearing on the random error or variability and that even though analyst was a significant factor on variability, the deviation from the mean so caused was only 0.3% and of no practical significance. When the systematic error introduced by the tolerance limits of the certified alcohol standards (purchased from the Laboratory of Government Chemists, UK) was taken into account, the total uncertainty (random plus systematic errors) of an alcohol determination at 99.5% confidence level was found to be 4%. It is recommended that laboratories engaged in blood alcohol determination should adopt similar statistical treatment of their analytical results to find out the error and to ensure that the results are independent of analyst and instrument used.     

Hair analysis by using radioimmunoassay, high-performance liquid chromatography and capillary electrophoresis to investigate chronic exposure to heroin, cocaine and/or ecstasy in applicants for driving licences

The present paper describes an integrated diagnostic strategy to check the physical fitness of subjects, formerly users of illicit drugs, to obtain a driving license, after having quit their addiction. According to the Italian law, applicants for a driving license with a history of drug abuse must give evidence to have quit this behaviour and to show no risk of relapse in the future. To prove this, at our institute, they undergo medical examination, hair analysis and a urinalysis program on eight seriate samples, collected over about 40 days. About 700 subjects per year are investigated with this strategy. The hair samples are screened for opiates (morphine), cocaine and ecstasy, the most abused illicit substances in our region, by using commercial radioimmunoassays adopting cut-off levels of 0.1 ng/mg. All positive samples and about 10% of negatives are confirmed by high-performance liquid chromatography. Further confirmation of results can be carried out by capillary electrophoresis (and/or GC/MS or MS/MS). In 1998, the prevalence of positives for morphine, cocaine and ecstasy was 4.8, 11.3 and 2.6%, respectively. In this year, for the first time, the percentage of hair samples positive for cocaine was greater than that for opiates. The results of this integrated diagnostic strategy are presented and discussed, with particular emphasis on the comparison between hair analysis on a single sample and seriate urinalyses (on eight samples).     

A biomechanical study of the human vertebral artery with implications for fatal arterial injury

We studied the biomechanical behaviour of ring and strip specimens from along the length of 18 vertebral arteries taken from 16 subjects aged 28-90 years, in order to consider some of the factors which may play a role in vertebral artery rupture. The method was chosen to allow a comparison between circumferential distension (ring samples) and longitudinal extension, (strip samples). The samples were extended between the jaws of a tensile testing apparatus until the specimen broke and a number of biomechanical parameters were derived. These were the percentage extension to break, the tensile strength, Young's modulus and the peak load. There were a number of important findings. The vertebral artery was shown to be susceptible to longitudinal stretching with a number of strip samples breaking when extended by as little as 16-20%. The tensile strength and load at peak of the strip specimens were correspondingly lower than for the ring samples. Marked intersubject variations were shown for all these parameters and prominent changes in behaviour occurred along the vertebral artery. This study indicates that the artery may be susceptible to head and neck movements which cause the vessel to stretch, and intersubject variations in behaviour may be one important explanation for the marked differences in outcome which appear to exist in subjects who suffer broadly similar head and neck insults.     

Unusual infant death: dog attack or postmortem mutilation after child abuse?

An unusual form of fatal child abuse is reported in which investigations by the police and the medical examiner were able to distinguish blunt force head trauma followed by postmortem dismemberment from a fatal dog attack. A discussion of the approaches used to ascertain the correct diagnosis is presented, as well as an overview of dog attacks on humans.     

Swiss Caucasian population data for the STR loci D2S1338 and D19S433 using the AmpFISTR SGM plus PCR amplification kit

Allele and genotype frequencies for the ten STR loci D3S1358, VWA, D16S539, D2S1338, D8S1179, D21S11, D18S51, D19S433, TH01, FGA were determined in a Swiss Caucasian population sample (n=206) using the AmpFISTR SGM Plus Amplification kit. Electrophoresis was carried out on an ABI PRISM CE 310 Genetic Analyzer instrument. Previously, allele frequencies were published for the 13 STR loci D3S1358, VWA, FGA, D8S1179, D21S11, D18S51, D5S818, D13S317, D7S820, THO1, TPOX, CSF1PO and D16S539 for the same samples (n=206) amplified with the AmpFISTR Profiler Plus and Cofiler PCR Amplification kits. Since the results for the eight loci D3S1358, VWA, FGA, D8S1179, D21S11, D18S51, THO1, D16S539 shared between the AmpFISTR SGM Plus, Profiler Plus and Cofiler PCR Amplification kits already are published, only the allele frequencies for the two STR loci D2S1338 and D19S433 are reported in this paper. The two loci meet Hardy-Weinberg expectations. In addition, there is little evidence for association of alleles among the 15 loci (amplified with the Profiler, Cofiler, and SGM Plus amplification kits). The allelic frequency data can be used in forensic analyses to estimate the frequency of a multiple STR locus DNA profile in the Swiss population.     

Delimitation of the time of death by immunohistochemical detection of thyroglobulin

To improve the possibilities to delimit the time of death after longer laytime it was examined if this is possible by immunohistochemical detection of thyroglobulin. The results show that in our examination material the colloid and the follicular cells of the thyroid glands of up to 5-day-old corpses produce a positive immunoreaction towards thyroglobulin in all cases whereas none of the corpses older than 13 days show such a reaction. This means that in case of a negative immunoreaction the time of death can be assumed to lie more than 6 days before the autopsy. The fact that a negative immunoreaction occurs consistently after 13 days leads to the conclusion that when thyroglobulin has been stained in a specimen, the death of the respective person must lie a maximum of 12 days earlier, whereby these time-limits may change in considerably different surrounding conditions.     

Immunohistochemical detection of methadone in the human brain

To develop a method of detecting methadone in the human brain by immunohistochemistry, brain tissue of frontal cortex, cerebellum, hippocampus, basal ganglions and brain stem from victims of a lethal methadone overdose was examined. The staining was performed with a monoclonal anti-methadone antibody from the mouse, originally developed for immunochemichal purposes (ELISA). With the help of the DAKO((R)) Catalyzed Signal Amplification (CSA) System, a specific positive immunoreaction was obtained in the neurons of the frontal cortex and hippocampus, as compared with specimen from deaths without exposition to methadone. Thus, along with metamphetamine, phenobarbital, morphine and insulin, immunohistochemical detection is also possible for methadone and the intake of this medicament can now be proven morphologically.