Role Of Forensic Toxicology Biology Essay

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During suspicious death investigations including suicides, forensic toxicology is often implemented to ensure lack of poisoning or impaired mental capabilities. The forensic toxicologist requires samples for possible drug or poison analysis from the pathologist, which are dependent on the availability and often due to a lack of communication, the correct specimens are not received, leading to an inability to perform correct analyses.

The standard array of samples for forensic toxicological analysis usually consists of urine, blood (whole blood, serum or plasma) and possibly gastric content (Brandenberger et al 1997). Urine is preferential for analysis of xenobiotic as it contains high concentrations (in comparison to blood) and possible metabolites and is usually available in large volumes (Flanagan et al 2007, Du Ponta et al 1995, Wolff et al 1999). Two 25ml samples of urine are required, one with 2% weight /volume fluoride as a preservative. Whole blood samples are required for detection of parent compound whilst blood plasma and serum are the norm for quantitative analysis, although blood volume can be limited (Flanagan et al 2007). Blood samples should be taken from the heart, vena cava or another convenient large vessel at a volume of 10ml, with fluoride/oxalate preservative if suspected alcohol usage (Flanagan et al 2007). In a case such as this, where the cadaver is in a less than preferential state leading to sample contamination, other specimens types maybe considered. The vitreous humour should be considered if there is a lack of urine, essentially it is a salt solution containing little protein, which the xenobiotic and metabolites can be extracted and analysed, it is also a suitable specimen for alcohol analysis (Flanagan et al 2007, Jones et al 2001, Wolff et al 1999). The eyes are often intact in a death such as this, providing an uncontaminated sampling site, although there is a limited volume and can be unpopular with relatives (Jones et al 2001). Both eyes should be sampled and stored separately with a sodium fluoride preservative (2%w/v). All samples should be stored at 4oC before transport with the exception of hair and nails that are stable at room temperature. If specimens are low in volume they are considered residual specimens and should be stored at -20oC due to decreased sensitivity and scope of analyses that maybe undertaken (Flanagan et al 2007). All specimens should be labelled and be kept in secure containers (Brandenberger et al 1997).

As alcohol, cocaine and clozapine were suspected to be present in the specimens due to the subjects history specific analytical techniques would have been performed as well as a broad screen for other illicit drugs or poisons. A basic screening for illicit drugs requires an extraction of possible xenobiotic from biological matrix, usually by liquid-liquid extraction (drug from aqueous solution to organic solvents) or solid-phase extraction (aqueous solution through disposable tubes packed with sorbent material) with liquid-liquid preferred as less time-consuming and more sensitive (Wolff et al 1999, Diamond et al 1996). The extracted sample is then analysed via an immunoassay with the standard being ELISA (enzyme linked immune-sorbent assay) as most cost effective and can utilise whole blood, serum, urine and hair (Simpson et al 1997). If there was a positive result this would have to be confirmed with a different assay with gas chromatography with mass spectrometry detection being the standard, but thin layer chromatography (TLC) or liquid chromatography (LC) also being implemented (Wolff et al 1999, Braithewaite et al 1995, Simpson et al 1997). Cocaine requires the same methodology as above, with liquid-liquid extraction, followed by GC-MS to identify and confirm presence of cocaine or metabolites including benzoylecgonine (BE) and norcocaine (Shaw 2001, Jenkins et al 1999). The analysis of ethanol differs slightly as a flame ionization detector is used instead of mass-spectrometry using either a direct injection or headspace technique sampling GC which is preferred for volatile samples as protects column from biological matrix (Kugelberg et al 2007, Brandenberger et al 1997, Shaw 2001).

The presence of ethanol in the urine and blood confirms consumption of alcoholic beverages, as specimen were taken very close to time of death meaning that alcohol generation or destruction during decomposition has not occurred (Shaw 2001, Jones 2000). Further analysis of the vitreous humour for ethanol will ensure lack of post-mortem diffusion due to distance from stomach and give a more realistic estimate of blood ethanol concentration perimortem (Jones et al 2001). BE is a metabolite of methylbenzoylecgonine (cocaine) and its presence in the urine and blood can confirm subjects consumed cocaine. Cocaine and subsequent metabolites are excreted by simple filtration into the urine, with up to 90% of dose excreted within the first day (Shaw 2001, Hamilton et al 1977). Even with knowledge of quantitative data of BE and cocaine the exact dose and timing of cocaine intake cannot be calculated but rough estimates can be produced to confirm if the subject was mentally impaired (Karch et al 1991, Shaw 2001). As there is confirmation of alcohol and cocaine usage, which combined with the history of alcohol and illicit drug abuse, could confirm suicide due to association of suicide and drug and alcohol abuse (Wilcox et al 2004, Lester 1995).

Clozapine is an anti-schizophrenia medication that has been associated with symptoms of dizziness and lightheadedness and seizures leading to a possibility of a fall from the multi-storey car park instead of a suicide (Medline Plus 2008). As no clozapine was found in the blood and urine this hypothesis can be rejected and the likelihood is that lack of schizophrenic medication lead to heightened symptoms and increased risk of suicide (Kreyenbuhl et al 2002). Clozapine does not instantly cause relief from symptoms and should not be abruptly stopped and patients should be weaned. To estimate when the subject discontinued treatment analysis can be performed on keratinaceous specimens such as hair as have a larger window of detection (Wolff et al 1999, Wennig 2000). The hair specimen must be taken directly from the scalp (10-20ng) as the concentration of drug will be highest here. The samples must be cut into centimetre sections to represent the months, these will be pulverised and subjected to either immunoassays or chromatography although GC-MS shows the highest sensitivity to the low concentrations present in the hair (Du Pont et al 1995, Wennig 2000, Flanagan et al 2007, Wolff et al 1999). There are interpretational difficulties analysing drugs within hair specimens, these can be due to rate of growth, cosmetic treatments, ethnicity, metabolism and bioavailability of the drug of interest, gender and inter-individual variability, all of which can lead to possible inconsistency within results found (Wennig 2000). Variations within hair growth have been recorded between 0.7 and 3.6cm a month, the mean of 1cm a month is the accepted rate, but this difference obviously leads to an estimation of the timing of drug intake (Wennig 2000, Moeller et al 1993, Wolff et al 1999). Hair analysis also only gives a vague timing of drug intake, given in intervals of months, which is a broad period of time. As there is a lack of a standardised analysis and interpretation, evidence found may be debatable (Du Pont et al 1997).

The absence of clozapine indicates the subject should have been experiencing schizophrenic behaviour combined with the presence of ethanol and benzoylecgonine showing usage of cocaine and alcohol suggesting the subject may have had a heightened schizophrenic state, leading to increased likelihood of suicidal tenancies. Including the history of the subject’s drug abuse, this could be interpreted as a suicide rather than a fall. This should satisfy relatives and have case ruled as a suicide.