Vidhyashree R, B.Sc. Forensic Science, RR Institute of Management Studies, Bangalore
Decomposing microbes are microscopic organisms that play a pivotal role in the natural process of
decomposition, that are found in Environment microbes such as bacteria, fungi, and corpses. Their
primary function is to break down organic matter, such as dead plants, animals, and other organic
substances, into simpler compounds. In forensic science, the study of decomposing microbes has
gained prominence due to their role in estimating the POSTMORTERM INTERVEL (PMI) and
providing additional evidence such as estimating the time since death more accurately. Microbes
can provide valuable information for determining geographical location in forensic investigations
through the analysis of microbial signatures associated with specific environments.
After death, the process of decomposition begins, facilitated by decomposing microbes, which
include bacteria, fungi, and other microorganisms.Decomposing bodies attract various insects,
including blow flies, beetles, and mites, which feed on the decaying tissue. These insects lay eggs
on or near the body, and their larvae (maggots) hatch and feed on the decomposing flesh.
Decomposing microbes play a crucial role in this natural process as follows:
1. Fresh Stage: Immediately after death, the body undergoes autolysis, where cells break down
and release enzymes. Decomposing microbes begin to proliferate, especially on external surfaces
and in orifices. Initially, aerobic bacteria dominate in the presence of oxygen, breaking down
sugars and proteins.
2. Bloat Stage: As anaerobic conditions develop due to the depletion of oxygen, anaerobic
bacteria thrive, producing gases like methane and hydrogen sulfide. This leads to bloating of the
body as gases accumulate within body cavities and tissues.
3. Active Decay Stage: This stage is characterized by the breakdown of tissues and organs as
decomposing microbes, primarily bacteria and fungi, consume organic matter. Proteins, fats, and
carbohydrates are broken down into simpler compounds, generating heat and causing the body's
temperature to rise.
4. Advanced Decay Stage: At this point, the body's tissues have largely liquefied, and the rate of
decomposition slows down. Decomposing microbes continue to break down remaining organic
matter, releasing nutrients and gases into the surrounding environment.
5. Dry Remains Stage: In the final stage of decomposition, only skeletal remains and dried skin
are left. Decomposing microbes continue to play a role in the degradation of remaining tissues,
albeit at a slower rate. The composition of microbial communities changes throughout the
decomposition process, with different microbial species dominating at each stage.
Throughout these stages, decomposing microbes facilitate the breakdown of organic matter,
releasing nutrients and gases into the environment. The process of decomposition is influenced by
factors such as temperature, moisture, oxygen availability, and the presence of insects.
Decomposing microbes contribute to solving crimes in forensic cases.
Estimating Postmortem Interval (PMI): By studying the microbial communities on
decomposing bodies, forensic scientists can estimate the time since death more accurately.
Geographical Location: Microbial signatures associated with specific environments can
help identify the geographical origin of a sample.
Identification of Human Remains: Changes in the human micro-biome during
decomposition can provide insights into the individual's health, lifestyle, and recent activities
prior to death.
Additional Evidence: Microbial evidence, along with other forensic evidence like DNA
analysis and insect activity, provides a more comprehensive picture of a crime scene.
Microbial signatures on evidence such as clothing, soil, or weapons can help link suspects to
crime scenes or establish connections between different pieces of evidence.
Enhancing Insect-based Evidence Analysis: Decomposing bodies attract various insects,
and the development and behavior of these insects can be influenced by microbial activity.
By studying the interaction between decomposing microbes and insects, forensic
entomologists can refine PMI estimates and provide valuable evidence to reconstruct crime
scenes.
Sample Collection: Forensic investigators collect samples from the crime scene, including
soil, vegetation, clothing, and bodily fluids or tissues, where decomposing microbes may be
present.
Microbial Analysis: Microbial analysis involves identifying and characterizing the
microbial communities present in the collected samples. This can be done using various
techniques such as DNA sequencing, microscopy, and culture-based methods.
Comparison to Reference Databases: Forensic scientists compare the microbial profiles
obtained from the crime scene samples to reference databases containing microbial data from
different geographic locations and environmental conditions. This comparison helps
determine if the microbial signatures are consistent with a particular location or environment.
In the "Bella in the Wych Elm" case, the discovery of skeletal remains inside a tree trunk in 1943
led to a long-standing mystery. While specifics of microbial analysis aren't documented, modern
forensic techniques, including microbial analysis, have been used to revisit the case. Though
officially unsolved, it highlights how forensic science, including decomposing microbes, aids in
investigating cold cases.By analyzing microbial communities associated with decomposition,
forensic scientists can estimate the postmortem interval more accurately, identify crime scenes, aid
in victim identification, and enhance overall investigative processes. Through techniques such as
DNA sequencing, microscopy, and comparative analysis, microbial evidence complements
traditional forensic techniques, contributing to the resolution of criminal cases worldwide. As
forensic science continues to advance, the role of decomposing microbes in solving forensic cases
is expected to grow, further highlighting their importance in the field of criminal investigations.
REFRENCES:
1. "composition: A Synthesis of Concepts and Processes" by Steven A. McMahon and others.
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