This essay has been submitted by a student. This is not an example of the work written by our professional essay writers.
Task) You are asked to analyse two blood samples for alcohol and comment on the results. One is from a motorist who was stopped by the police for driving erratically. The other is from a male who was stabbed to death and whose body was found in a heated room approximately 3 to 4 days after death. Compare and contrast how you would assist the police in these two circumstances.
Amongst all drugs, alcohol, specifically ethanol, is the most commonly used and although legal (usually age regulated), it has one of the highest crime and death rates, (if including alcohol-related incidences) therefore has a major impact on society (Brandenberger et al 1997, Sjogren et al 2000, Kugelberg et al 2007). In the U.K during 2009 there were a total of 8,664 alcohol related deaths (National Statistics 2010), thus the ability to quantify concentration of alcohol consumed (usually via blood alcohol concentration (BAC)) is vital and accuracy is imperative as convictions are based upon these results (Leikin et al 2003). Inebriation combined with vehicles leads to high levels of traffic accidents and fatalities, which has led to strict laws on the subject (Mast et al 1999, Kugelberg et al 2007). There are also higher levels of crime to consider, liability of accidents and life insurance pay-outs (if inebriated and accidental death occurs many policies are void) (Kugelberg et al 2007, Jones 20002, Jones 1998). The liability of these accidents is often dependent on whether the offender has been mentally impaired (due to ethanol) (Rivara et al 2000). Thus alcohol analysis performed by the forensic toxicologist must be precise and accurate.
Ethanol has acute and chronic toxicity, with the acute being the most relevant for law enforcement. At concentrations above 0.5% (g\kg), the subject will experience decreased capacity for concentration and mental observation, leading to a decreased capability to perform normal tasks, including driving (Kugelberg 2007, Jones 20001, Jones 20002, Shaw 2001). As ethanol concentration increases these symptoms are heightened as well as decreased power of judgement, vision and walking capacity, leading to the possibility of impaired judgement and mental capabilities, therefore quantification is essential for conviction (Bradenberger et al 1997, Church et al 1997). Often there can also be temporary amnesia, which is regularly used as a defence at trial or possible alcohol-induced mental impairment (Harrell 1981, Lester 1995). Statistically, for minor offenses the use of alcohol usually increases the severity of the sentencing, but the opposite is observed for more serious crimes such as murder (Harrel 1981).
The universal standard analytical method for quantification of ethanol in blood samples (or other biological specimens) is gas chromatography with a flame ionisation detector (Bradenberger et al 1997, Kugelberg et al 2007, Jones 1998, O'Neal et al 19961) The whole blood sample can be injected directly into the column (direct injection) but head-space sampling (HS-GC) is preferred for volatile substances such as alcohol, as this protects the column from the matrix with n-propanol as the internal standard(O'Neal et al 19961, Bradenberger et al 1997, Kugelberg et al 2007).
The legal U.K limit for alcohol concentration whilst driving is 350mgL-1 breath or 800mgL-1 blood. Thus any traffic crime, where alcohol use is suspected, biological samples must be analysed to ensure above this (Road traffic act). Two samples are taken from the offending driver, these can be two breath specimens, but typically one breath and one blood specimens are procured (can be urine but uncommon) (Jones 1998, Road traffic act, Taylor et al 2006). In a suspected drunk-driving offence, such as the case above, a breath sample is normally performed at road side by the arresting officers. This is known as point of care testing (POCT), the obvious advantages to a test such as this, are economical (inexpensive) and the rapid turnaround time, which is almost instantaneous (Shaw 2001, Church et al 1997). Law enforcement use infra-red breathalyser due to the stringent requirements of law for evidential testing (Brandenberger et al 1997, Shaw 2001).These utilise two or three wavelengths that are significantly absorbed by ethanol. Although these are not unique to ethanol, the likelihood of interferrants in breath is minimal. Problems can arise due to acetone interference in diabetics, law enforcement should be aware of this and further blood analysis would see a BAC of zero (Jones 20002, Taylor et al 2006, Shaw 2000). A secondary confirmatory assay is performed for conviction, with the lower value being the prosecutable concentration (Road traffic act, Taylor et al 2006). The blood analysis will give an exact BAC and law enforcement will be able to prosecute from this. Police should be aware that recent consumption of alcoholic beverages, use of breath fresheners and asthma inhalers, burping and vomiting can all lead to false-positives in the breathalyser tests (Taylor et al 2006).
To competently quantify a person's blood alcohol concentration (BAC) at time of death to identify possible inebriation can be problematical, especially when the cadaver has been left for some time before samples are taken, as in the case above (Kugelberg et al 2007, Jones 20001, Jones 1998, Videira de Lima et al 1999, Luikin et al 2003). Qualitative and quantitative analysis of BAC is now routine, but problems remain in interpretation of these results. (Kugelberg et al 2007, Jones 20001, Church et al 1997) Interpretational issues are due to possible production, destruction or migration of ethanol within the cadaver. Changing or high BACs can be misleading, giving the assumption that the subject was inebriated perimortem (Kugelberg et al 2007, O'Neal et al 20062, Leikin et al 2003, Videira de Lima et al 1999). Ethanol production during decomposition due to microbial activity and glucose fermentation is expected (O'Neal 19962, Kugelberg et al 2007). This production is increased by environmental conditions and length of time from death to autopsy, such as the case shown above. To stop further ethanol production the preservative sodium fluoride 2%w/v is added to samples, which act as an enzyme inhibitor (O'Neal et al 19962, Videira de Lima et al 1999, Jones 20001). Ethanol can diffuse from the stomach into the peripheral blood, giving a higher BAC than at time of death, if expected sampling must allow for this, with several blood samples at different sites and possibly urine or vitreous humour sampling (O'Neal et al 19962, Kugelberg et al 2007). The vitreous humour is an appropriate specimen for alcohol analysis and the large distance from stomach reduces risk of diffusion and gives a more realistic estimate of BAC perimortem (Videira de Lima et al 1999, Kugelberg et al 2007, Jones 2001). The specimens given can also be contaminated by solvents used in life-saving treatment (Kugelberg et al 2007). There is a significant change in the analysis of the ethanol, in that t-butanol is used as an internal standard for GC, owing to n-propanol being produced, albeit in small quantities, in putrifaction of the cadaver (Kugelberg et al 2007). The BAC value given from post-mortem forensic analysis will be interpreted by the forensic toxicologist considering the possible post-mortem changes, giving an estimation of the perimortem BAC and possible alcohol-induced mental impairment giving law-enforcement a reliable estimation. Law enforcement should be aware of the differences in sampling techniques, blood should be taken from femoral vein will be homogenised due to coagulation, also that the vitreous humour maybe sampled (Kugelberg et al 2007, O'Neal et al 19961, Jones 20001, Jones 2001).
There are major differences between a forensic and criminal investigation, for example the cases shown above, and the role of the forensic toxicologist will alter to suit this. The samples origin will be different for a cadaver compared to that of a living person. The analysis performed for alcohol quantification will be identical (GC-HS) in blood and urine. But there will be differences in the interpretation of these results. In the fatality the concentration of alcohol will suggest possible circumstances of the assault (stabbing) or possible homicide, perhaps giving an insight into the mental capabilities and potential lack of judgement, giving law enforcement possible scenarios for the time before death. In the traffic incident the BAC will have to be compared to that of the breathalyser result to look for correlation and if there is too large a margin, it may need to be considered that there was possible interferrants. The law requires there to be extreme precision and specificity with the alcohol quantification as the results found will be used for prosecution and therefore possible loss of driving licences, fines, prison sentences, and loss of integrity of the person being accused (especially due to some religious beliefs). These differences will have to be explained to law enforcement and to a jury in court, with possible difficulties underlying in explanation of changing alcohol concentrations after death.