This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: New research reveals that microbial clocks—forensic tools that track the succession and development of bacteria and fungi involved in decomposition after death—are highly accurate for estimating time since death, or postmortem intervals (PMIs), across different environments and between pigs and humans. Data collected from pigs in the U.K. successfully estimated the PMI of human bodies placed in the U.S.
For the first time, this showed that microbial data from different species can accurately and reliably estimate time since death in human forensic investigations. The research, published in Scientific Reports, assessed bacteria found both inside and outside the noses of pig carcasses as they decomposed outdoors during summer in the U.K. Before this study, there had been limited research in the U.K. on the relationship between PMIs and microbiomes (community of microorganisms) across different environments.
Most research to date has been conducted in controlled laboratory conditions using mice or in warmer outdoor climates in the U.S., limiting its applicability to the U.K. Although studies have used both animal and human models, few have examined whether findings from animals can be reliably applied to humans. This study provides new insights into the potential for animal-derived microbial data to support human forensic investigations.
The study, led by Professor Noemi Procopio from the University of Lancashire in collaboration with the University of North Dakota, analyzed the community of organisms in the nostrils and respiratory passages of pig carcasses exposed to outdoor summer conditions in the U.K. It builds on research from last year that analyzed communities in North Dakota. A total of 312 nasal-swab samples were collected from three pig carcasses across 26 time points.
The researchers then tested their model on a separate data set from 36 human bodies across three parts of the United States and over four seasons to see whether the model worked reliably in different locations. The findings showed that increased insects and flies feeding on the dead bodies introduced new bacteria and changed the bacteria already present. Environmental conditions—particularly temperature and insect accessibility—strongly affect decomposition rates and microbial activity.
Results accurately demonstrated that higher temperatures accelerate microbial metabolism and succession, while colder climates slow them down. Noemi Procopio, professor of forensic science at the University of Lancashire, said, "Microbial clocks have the potential to give forensic investigators a more accurate understanding of the time since death. By examining changes across different areas of the body, including the skin, nose, mouth and ears, we can track how microbial communities change after death and estimate the time since death with high accuracy.
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