Overview of Forensic Limnology and Case Study
Limnology is the study of biological, physical and chemical features of a water body. The study of inland waters (lakes, reservoirs, streams, marshes, ponds, rivers, groundwater) as an ecological system interacting with their drainage basins and the atmosphere. Forensic limnology is the study of water ecology in legal matters; such as deaths caused by drowning.
In drowning cases the water enters the alveolar spaces of the lungs. This causes hypoxia (lack of oxygen in the body) and death. The body is heavier than water and drowns but when the decomposition starts it causes gas production, which causes bloating and the body starts to float on the surface. One of the signs of drowning is that a large amount of froth is present near the mouth and the nostrils in a freshly drowned body. It is because of the air passages. The skin gets wrinkled and pale. The skin layer of the hands and the feet’s starts to detach. The lungs get heavier due to the water and the blood vessels break down.
Diatoms are microscopic unicellular algae that are present in aquatic habitats. They are made of silica and are less than 200 microns in size. They vary in terms of shape, size and structure and are very valuable forensic evidence. They are so small that people are unable to notice them and can be preserved for a longer period of time. They live near the places where they get enough sunlight and often get attached to the edges rather than floating.
In forensics, diatoms are used to pinpoint the drowning site. Whether the body drowned somewhere else or in the same location where it was discovered. The PMSI (post mortem submersion interval) is also provided.
In person who is already dead and later falls into water, the diatoms in the water enters in unsterile parts of the body (where they can easily enter) but when the person dies due to drowning, they are deposited in the sterile parts of the body (bone marrow in the femur and sternum and brain).
Drowning Investigation: -
They play an important part in drowning-related investigations. They can shed light on the circumstances surrounding a drowning by looking at things like water temperature, depth, currents, and the existence of aquatic vegetation and wildlife. They may determine whether the body was transferred after death or if it was submerged for an extended period of time. The death caused by drowning is referred to as antemortem drowning. In contrast, death occurs prior to entering the water, or the body is discarded after homicide, which is referred to as postmortem drowning.
Diatom Identification: -
Diatoms are a diverse group of organisms, with many species exhibiting various physical traits. Diatoms can be identified and classified based on their forms, sizes, and ornamentation. This identification can aid in the connection of a specific water source to evidence, such as drowning victims, crime scenes, or things retrieved from bodies of water. Water containing diatoms can only enter the lungs passively in situations of postmortem drowning and it does not reach other peripheral organs since the alveolar wall does not break down, and there is no breathing and no circulatory system. As a result, even if they are present in the lungs, they cannot spread to other organs. As a result, the presence of diatoms in peripheral organs is a classic indicator of antemortem drowning.
Sediment and Soil Analysis: -
Diatoms may also be found in crime scene sediments, soil or residues, as well as on criminally involved artefacts. These diatoms can be analysed to assist link artefacts to specific locations or provide information about the flow of evidence.
Time of Submersion: -
Diatoms are extremely sensitive to changes in their environment. Diatomic species differ not just from one site to the next, but also due to seasonality. This is because of temperature, salinity, pH level, nutrition availability and vegetation all play important roles in diatom survival and tolerance in aquatic bodies. All of these variables contribute to the survival of diatoms in that water source.
Case Study: Two Young Boy At Connecticut Pond— Reel Danger
(https://forensicreader.com/reel-danger-case/)
Incident:
In July 1991, a disturbing incident occurred in suburban Connecticut, where two young boys were subjected to a brutal attack by multiple teenage assailants while fishing at a local pond. The victims were initially confronted at knife point, subsequently bound with duct tape, physically assaulted with a baseball bat, and forcibly taken into the pond with the intent to drown them. However, one of the victims managed to free himself, rescue his companion, and seek help from nearby residents. The incident led to a thorough investigation that swiftly resulted in the identification and arrest of three suspects.
Findings:
To link the suspects to the crime scene, law enforcement authorities seized sediment-encrusted sneakers from both the assailants and the victims. These sneakers were then subjected to analysis for aquatic microorganisms. The analysis revealed the presence of numerous species of diatoms (microscopic algae) and scaled chrysophytes (planktonic algae) on the sneakers. Additionally, reference samples of sediment from the pond were also examined. The key discovery was that the algal communities found on the sneakers closely matched those present in the pond, strongly suggesting exposure to a common freshwater habitat, which was likely the very pond where the crime had taken place.
Investigation:
Further investigations into the algae revealed that a particular species, Mallomonas caudata, dominated in each sample. Moreover, the ratios of three species of the diatom Eunotia were consistent across all samples, indicating a high degree of similarity. These findings provided strong evidence that all of the samples, from the sneakers and the pond sediment, likely originated from the same, if not a highly similar, location.
Conclusion:
In summary, this case is a compelling example of how the field of forensic limnology, which involves the study of aquatic ecosystems and their microorganisms, was employed to support a criminal investigation. By analyzing the algae found on sneakers and comparing them to those in the pond, investigators were able to link the suspects to the aquatic crime scene, helping to strengthen the case against them. This case underscores the practical application of aquatic community ecology in forensic investigations.
INDIAN Case Study : https://zenodo.org/records/47968
CONCLUSION :-
Forensic limnology is a very helpful branch which makes us understand whether the death was a suicide or murder. So many people are not aware about the diatoms present near the water's surface and hence think that they can get away with the crime. Forensic limnology provides direction to the investigator. It is a very cornered branch which is not very mainstream. It is important to highlight this branch and educate people about it so that there won't be any shortage of people working in it.
References :-
- https://www.studocu.com/en-gb/document/keele-university/forensic-geoscience/forensic-limnology-lecture-notes-4/16717711
- https://en.wikipedia.org/wiki/Forensic_limnology
- https://www.zeiss.com/microscopy/en/applications/forensics/entomology-limnology.html
- https://simplyforensic.com/forensic-limnology/how-do-diatoms-aid-forensic-science-in-solving-a-crime/
- https://forensicreader.com/famous-cases-related-to-diatoms/?expand_article=1
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