Estimating the time of death of a body is a complex process and even with advances in forensic science an exact time cannot be determined. A pioneering approach uses the human microbiome (the collection of microorganisms within a given ecological niche of the body) to determine how long a deceased human has been dead for. The microbiome of the cadaver had been dubbed the “necrobiome.” A decomposing corpse becomes its own mini-ecosystem, hosting insects, scavengers and multitudes of microbes. It is the microbes that have sparked recent research interest.
The research has been led by Dr. Nathan H. Lents of the John Jay College of Criminal Justice, City University of New York, and it is based on the microbial analysis of dead bodies. For the research, the science team looked at the microbial content of ear and nasal canals of 21 cadavers. To determine the microbial changes, the researchers took samples through several weeks of decomposition.
The microorganisms isolated were studied by Next-Generation metagenomic DNA sequencing, this allowed populations and species variation to be assessed. The primary aim was to track the microbial changes against time.
Once the data was collected, the researchers put together a statistical model and this allows for a prediction to be made about the amount of time that has passed since a person died. The accuracy is down to two days for bodies that are several weeks old. The approach is based on understanding which microorganisms differ on a dead body compared with a living person and then understanding how long the microorganisms take to spread through the deceased body.
Discussing the research further, Dr. Lents said: “Our approach had the benefit of sampling the same cadavers repeatedly as they decomposed and we think that this really added to the ability of our machine learning approach to see through all of the massive amount of noisy data and detect the underlying patterns.”
The researchers hope to undertake further research to try and improve the accuracy of the data and also to see if geographical variations affect the microbial profile. They hope the findings will be useful for crime scene investigations.
The research has been published in the journal PLOS One, titled “A Machine Learning Approach for Using the Postmortem Skin Microbiome to Estimate the Postmortem Interval.”
