<![CDATA[Introduction: The Ciliwung River is frequently reported as a location of drowning cases in Indonesia. Variations in aquatic environmental conditions along the river are presumed to influence the rate of postmortem tissue decomposition, which plays an important role in postmortem interval estimation in forensic investigations. However, empirical data regarding tissue decomposition rates in tropical aquatic environments remain limited. Purpose: This study aimed to determine and compare the decomposition rate of beef as a postmortem decay model in the upstream, midstream, and downstream segments of the Ciliwung River. Methods: This descriptive experimental study used 30 beef samples measuring 2×2×2 centimeters with an initial weight of 9.3 grams. The samples were divided into six groups, consisting of two control groups and four treatment groups based on water sources from different segments of the Ciliwung River. Observations were conducted over a 10-day period at 24-hour intervals, assessing changes in color, odor, texture, and mass. Water microbiological analysis was performed using the Most Probable Number method to determine fecal coliform and total coliform levels. Results: The fastest decomposition rates were observed in the second midstream and downstream segments, whereas the upstream segment exhibited the slowest decomposition. Higher coliform levels were correlated with accelerated decomposition. Conclusion: Decomposition rates differed among segments of the Ciliwung River and were influenced by aquatic microbiological conditions. This study provides preliminary data to support postmortem interval estimation in forensic investigations within tropical aquatic environments.]]>
