Vitreous humor is preferred over serum for postmortem potassium estimation to determine time since death. The principal reason for this preference is:

• A Vitreous potassium rises faster than serum potassium after death
• B Vitreous potassium concentration does not change after death
• C Vitreous is more protected from putrefaction, decomposition, and haemolysis, giving more reliable results ✓
• D Serum potassium falls after death making it useless for timing

Explanation

The vitreous humor is enclosed within a relatively rigid ocular globe, protected from haemolysis, microbial putrefaction, and environmental contamination that rapidly affect blood. Both vitreous and serum potassium rise after death due to cell membrane breakdown, but vitreous values are more consistent and reproducible, making them more reliable for time-since-death estimation. Serum potassium is unreliable due to haemolysis artefact rather than a fall in concentration.

Reference: The Essentials of Forensic Medicine and Toxicology (Narayan Reddy), 34th ed.

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Written and medically reviewed by the StethoPrep medical team.