A vitreous sample shows a potassium concentration of 3.2 mmol/L, close to the normal living range. Regarding the postmortem interval, the MOST reasonable inference is:
- A Death occurred at least 48 hours earlier
- B Death occurred very recently, likely within the first few hours ✓
- C The sample was contaminated with aqueous humour
- D The deceased had chronic renal failure
Correct answer: B. Death occurred very recently, likely within the first few hours
Explanation
Ante-mortem vitreous potassium is approximately 2.5 to 3.5 mmol/L, and the concentration begins climbing soon after death as intracellular potassium leaks out. A value still within the living range therefore indicates a very short postmortem interval, generally only a few hours. Contamination with retinal tissue raises potassium rather than lowering it toward normal, renal failure does not lower vitreous potassium, and 48 hours would predict a value far above baseline.
Reference: Knight's Forensic Pathology, 4th ed.
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Written and medically reviewed by the StethoPrep medical team.