I Smell Dead People
By Stephanie Wasiuk, Biology, 2018
Some may find it surprising how useful it is to know what a decomposing human body smells like and what exactly it is that makes it smell that way. Besides a putrid odor, the “smell of human death” is a major component of searching for bodies in forensic science as well as during natural disasters.
Cadaver dogs are mainly trained using two compounds — cadaverine and putrescine –their names hint at where they might be found and what they smell like. These two compounds are byproducts of the chemical breakdown of amino acids. In addition to being found in dead animals that have begun to decompose, these compounds are actually present in living animals, giving urine part of its distinctive scent. Forensic scientists are beginning to question the effectiveness of these two compounds and are in search of more specific human markers that may be present in cadavers.
Recently, a team from the University of Leuven in Belgium pursued this question, leading to a six month study to find out if there are indeed any chemical markers specific to human bodies as they decay. This team was not the first to investigate the scent of death, but they approached it in a more controlled manner than had been done before. In previous studies, researchers studied components of decaying flesh in outdoor environments, making it difficult to compare results as there are so many varying factors in an uncontrolled, outdoor environment.
To start from the very beginning, the Belgian team created a standard laboratory environment in which to analyze the decomposition of six human and 26 nonhuman sets of remains. Each sample was placed in a jar, complete with a sealable hole through which air samples could be extracted. The lids of the jars containing the samples were not airtight, allowing oxygen to flow into the jar which contributes to aerobic decomposition. An empty jar was also placed in the same room as those containing samples in order to serve as a control for comparison.
Samples of the components released by the tissues were collected at various times throughout the six month experimental period, often during the initial weeks, later decreasing to once a month during the last two months. These samples were analyzed using a thermal desorber with a gas chromatograph and mass spectrometry to identify any volatile organic compounds (VOCs). Over 450 VOCs were detected, including ones from the outside laboratory environment as well as from the jars themselves.
The results were less definitive than the team had hoped. They found eight compounds, including ethyl propionate, pyridine, and 3-methylthio-1-propanol, that distinguished humans and pigs remains from the remains of mammals, like mice, cows, deer, dogs, and rabbits. They were, however, able to distinguish human VOCs from pig VOCs based on a different group of five esters.
The research team observed some other trends as well. For example, sulphur-containing compounds were only present at detectable levels for the first three months, diminishing thereafter. Other compounds didn’t even register until the later part of the experiment. It was also acknowledged that in real situations, aspects like temperature, moisture, and even the type of soil in the area can affect the decomposition process and how these VOCs may be released.
More research is required to confirm both that the compounds identified do indeed indicate the presence of human remains and to search for any environmental factors that could change how these compounds are detected. This is a major step towards improving the approach to cadaver dog training as well as potentially creating a new technology that can detect these compounds. This team, as well as others around the world are looking into these questions, understanding their importance to forensic science.
All teams involved in this research are hopeful that the conclusions drawn from various experiments will allow a faster, more efficient way to recover bodies in times of natural disaster and to solve crimes.
Even though it may seem odd to seek out what makes dead bodies smell the way they do, especially when the experiments can’t be pleasing to the nose, there is a huge benefit to having the data and making use of it.
PLOS ONE (2015). DOI: 10.1371/journal.pone.0137341.