Postmortem vitreous potassium rises predictably after death. A vitreous K+ of 14 mEq/L is measured. Using the Sturner-Gantner formula (PMI in hours = 7.14 × K+ − 39.1), what is the estimated postmortem interval?
- A Approximately 61 hours ✓
- B Approximately 19 hours
- C Approximately 40 hours
- D Approximately 10 hours
Correct answer: A. Approximately 61 hours
Explanation
Applying the Sturner-Gantner formula: PMI = 7.14 × K+ − 39.1 = (7.14 × 14) − 39.1 = 99.96 − 39.1 = 60.86 ≈ 61 hours. Vitreous potassium is the most reliable biochemical marker for PMI estimation because the vitreous is sequestered, making it resistant to contamination by putrefactive changes that affect blood. The rise occurs at approximately 0.17 mEq/L per hour after an initial 10-hour stabilization period. Options A, C, and D correspond to incorrect arithmetic results and do not match the formula output.
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.