The Smell of Death: Confirming Decomposition using Volatiles in the Air

Odour mortis, or the ‘smell of death’, refers to the chemicals released from the body during decomposition. Renowned forensic anthropologist Arpad Vass, who has studied the chemical changes occurring in the body after death for many years, recently shared the details of a particularly interesting scenario. The article, published in the May 2019 issue of Forensic Science International, details a fascinating case in which the occurrence of human decomposition was demonstrated based solely on chemical compounds in the air for the first time, without any human remains actually being found at the scene. The article doesn’t specify suspect or victim details, but anyone familiar with the case will recognise it instantly.

First, a brief introduction. In 2008, a woman was charged with the murder of her daughter, allegedly storing the victim’s body in the boot of her car for several days before disposing of the remains and dumping the car. Police had initially been alerted to the incident by the suspect’s parents, who had picked up their daughter’s abandoned car and noticed a foul decomposition-like odour coming from the vehicle. Coupled with the fact they had not seen their granddaughter in several weeks, the suspect’s mother promptly called 911.

The police soon took possession of the car and agreed that the scent of decomposition was emanating from the vehicle. Numerous cadaver dogs, specifically trained to detect odours from decaying bodies, alerted to the back of the car, further suggesting some kind of decomposing remains had been stored in the boot of the car. Fly pupae were also discovered. Entomological evidence is frequently associated with decomposing human remains, with flies and various other insects known to visit corpses to feed or lay eggs. Although no human remains were found in the car, several weeks later the body of the missing girl was found in a wooded area near the suspect’s home, and the case promptly turned into a murder investigation, with the victim’s mother as the prime suspect. However with minimal physical evidence linking the body to the suspect’s car, law enforcement turned to a somewhat unconventional tool to aid their investigation.

Various pieces of evidence were recovered from the vehicle, including segments of carpet, scrapings from the tyre wells, and various pieces of rubbish found in the car. Interestingly, investigators also collected some air samples from the boot of the car. Air can be sampled from remote locations using a technique that utilises air pumps to draw in gaseous analytes from the environment and capture them in a sorbent trap. This collection of trapped compounds can then be transported to a laboratory for analysis. In this case, about 35L of air was collected from the vehicle into a type of sorbent tube, then analysed using gas chromatography/mass spectrometry (GC/MS). GC/MS is a well-established analytical technique, allowing scientists to separate the individual chemicals in a mixture and identify those components. You can read more about how mass spectrometry works here.

This process allowed researchers to figure out exactly which volatile chemicals were present in the suspect’s vehicle and establish whether these are everyday compounds likely to be found in a car, or if they had some other source.

In the years leading up to this case a great deal of research had been conducted at the University of Tennessee’s Anthropological Research Facility. At this facility researchers were investigating, among other things, the odours produced during the decomposition of a human body. The odours created during this process are the result of volatile compounds produced as the body decomposes, and research has demonstrated that hundreds of individual chemical components are formed during this complex process. As part of research at the university, researchers had constructed a vast database of hundreds of chemicals detected during the process of human decomposition, including the different decomposition stages at which those chemicals appear. By comparing the chemicals detected in the vehicle with those stored in the database, it was possible to identify compounds known to be produced during the decomposition process. There was an 80% match between the compounds detected in the boot of the car and those chemicals considered to be relevant to human decomposition. Furthermore, unusually high levels of chloroform were also detected in the boot of the car.

The results from the air samples collected and chemical extracts from various other artefacts in the car led the researcher to conclude that there was a very high likelihood of a decomposition event occurring in the boot of the car. Many of the compounds detected in the vehicle could only be logically explained by the presence of decomposing remains.

Despite these findings (and various other pieces of evidence presented in court), the jury reached a verdict of not guilty for the charge of murder. Not too surprising an outcome, considering the use of air analysis to detect decomposition had not previously been used in a legal investigation. However in closing arguments, the defence stated that the victim had in fact been placed in the vehicle for transport (claiming the victim’s death had been accidental), ultimately confirming the results of the analysis.

 

Vass, A. A. Death is in the air: confirmation of decomposition without a corpse. Forensic Sci. Int. (2019). doi:10.1016/j.forsciint.2019.05.005

Vass, A. A. Odor mortis. Forensic Sci. Int. 222, 234–241 (2012).

 

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Saliva for Cracking Down on Drink-Drivers

Saliva for Cracking Down on Drink-Drivers

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.

booze

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.

References

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