The intake of alcohol for leisure is common all around the world, and many of us indulge every now and then (some more so). But we’re all also aware of the effects of alcohol and how it can play a big part in criminal activities, ranging from drunken street brawls to homicide. In fact according to the National Council on Alcoholism and Drug Dependence, in the case of 40% of convicted murderers in the US alcohol was a factor in the crime. But of course most commonly in legal investigations, focus on alcohol consumption is most commonly related to driving.
In the United Kingdom, people suspected of drink-driving are typically pulled over and breathalysed at the roadside. If they fail the test (i.e. they are over the legal limit of 80mg per 100ml of blood), they will be taken to a police station and breathalysed once again. Typical breathalysers work by measuring the concentration of alcohol in a person’s breath (note I say in their breath, not strictly their bloodstream – two very different things). After consumption, a certain amount of alcohol will leave the body via the breath, thus allowing us to pretty accurately calculate a person’s blood alcohol content.
But a primary disadvantage of the breathalyser test is that it cannot be repeated. Once the alcohol is out of the individual’s system, the proof of their blood alcohol content is gone. And as with many types of scientific analysis, a certain margin of error will exist. Furthermore, what if a breathalyser test is simply not plausible? Either because the suspected drink-driver is not able to provide a breath sample or they are making all attempts possible to avoid it (a certain Brighton-based woman who continued to have an alleged panic attack to avoid giving a sample, for instance). In short, there are numerous flaws in the use of breathalysers, and there’s no chance of an accurate retest further down the line if for whatever reason the original sampling comes under scrutiny.
But what if a biological sample could be collected at the time, stored and subjected to future analysis as needed, and even repeat measurements taken if required? A blood sample is surely perfect for this. But on the other hand, this is a fairly invasive procedure that will not necessarily be appropriate in all situations. How about a simple saliva swab?
A number of healthy subjects ingested enough beer to achieve 0.5g ethanol per kg of body weight, after which saliva, urine and breath samples were collected at 10, 30, 60 and 90 minute intervals following alcohol intake. The breath samples were taken using a standard breathalyser, and bodily fluids were subjected to analysis by gas chromatography with a flame ionisation detector (GC-FID). The results correlated well, indicating that the analysis of saliva could well be a suitable alternative for monitoring the alcohol levels in individuals.
The use of saliva to test alcohol levels is not strictly novel, as there are alcohol test strips available for use with saliva. However as with most tests such as these, they are simply presumptive, meaning some additional form of analysis is required for confirmation. But a procedure involving the immediate collection of a sample that can be stored for future analysis along with a confirmatory analytical technique such as gas chromatography can instil more confidence in both drink-driving scenarios and numerous other medico-legal situations.
Bueno, L. H. P. et al. Oral fluid as an alternative matrix to determine ethanol for forensic purposes. Forensic Sci. Int. 2014 (242), pp. 117-222.
National Council on Alcoholism and Drug Dependence. Alcohol and Crime. [Online][Accessed 30 November 2014] Available from: https://ncadd.org/learn-about-alcohol/alcohol-and-crime
Pingback: Recent forensic science news and cases from around the world | FORENSICS in FOCUS @ CSIDDS | News and Trends