Forensic limnology

2. • Forensic limnology is the study of aquatic
ecosystems in order to obtain evidence for
criminal investigations.
• Forensic limnology is a sub-field of
freshwater ecology, which focuses especially
on the presence of diatoms in crime scene
samples and victims.

4. Autopsy and Sample Collection:
• Conduct a thorough autopsy on the drowned body.
• Collect biological samples, including lung tissues,
bone marrow, or other potentially diatom-
containing fluids.

5. • Five grams of marrow should be taken from a
victim to be placed in a nitric acid solution and
then burnt in a furnace allowing the release
of diatoms to then be analyzed. whether the
body was drowned before or after death.
.
• In these medico legal cases, presence of
diatoms in the body tissues is very useful
evidence.

6. • Identification of Potential Entry Points:
⚬ Determine likely entry points for water
into the body during drowning.
⚬ Focus on areas such as the respiratory
and digestive systems.
• Collection of Biological Samples:
⚬ Collect control samples from the water
body where the drowning occurred.
⚬ Sample water near the incident site to
represent the environmental conditions.

7. • Laboratory Preparation:
⚬ Transfer the collected biological and control
samples to a forensic laboratory.
⚬ Ensure proper chain of custody to maintain
evidence integrity.
• Diatom Extraction:
⚬ Use specialized techniques to extract diatoms
from the biological and control samples.
⚬ Chemical treatments may be employed to dissolve
tissues, leaving diatoms intact.

8. • They specifically used Nitric Acid Digestion as the
method for analysis of diatoms. They used the
sternum, clavicle, femur, and lungs of the bodies for
the purpose of their analysis. The samples were put
into nitric acid and left for about 12 hours and then
boiled for about half an hour after that.
• Multi-acid digestion uses a combination of
• HCl (hydrochloric acid),
• HNO3 (nitric acid),
• HF (hydrofluoric acid),
• HClO4 (perchloric acid).
• Because hydrofluoric acid dissolves silicate minerals,
these digestions are often referred to as 'near-total
digestions'.

10. • The liquid containing diatoms is examined on standard
slides using light or electron microscopy. Finally, the
diatom species and their abundance are compared
with suspect water samples to confirm the crime
scene
• Microscopic Examination:
• Examine the purified diatom samples under a
microscope.
• Identify diatom species based on their distinct shapes,
sizes, and markings.

12. • Extract and purify diatoms from the control sample using similar laboratory procedures as
for the victim's sample.
• Comparative Analysis:
• Conduct a detailed comparative analysis between the diatom samples from the victim and
the control sample.
• Look for matching species or unique characteristics.
• Different types of diatoms can also be used to identify the properties of a sample's
ecosystem. For example, a higher ratio of periphytic diatoms (i.e., those that are attached to
a substrate), the higher the vegetation concentration, and the shallower the water.

14. • Forensic limnology involving diatom
collection is a meticulous process that spans
from autopsy and sample collection to
detailed microscopic examination and
comparative analysis.
• Each step is critical for establishing a
connection between a drowned victim and
the specific aquatic environment, providing
valuable forensic evidence in legal
investigations.

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