A new biochemical method for estimation of postmortem time

Area of Science:

• Forensic Science
• Biochemistry
• Postmortem Interval Determination

Background:

• Potassium levels in vitreous humor are traditionally used to estimate postmortem intervals.
• Hypoxanthine (Hx), a degradation product of adenosine monophosphate (AMP), also changes after death.
• Antemortem hypoxia can affect Hx levels, complicating its use in forensic analysis.

Purpose of the Study:

• To compare the reliability of hypoxanthine (Hx) and potassium levels in vitreous humor for determining postmortem time.
• To investigate the influence of postmortem temperature on Hx and potassium concentrations.

Main Methods:

• Vitreous humor samples were collected from 87 subjects with known time of death.
• Bodies were stored at four different temperatures (5°C, 10°C, 15°C, 23°C).
• Hypoxanthine was measured using High-Performance Liquid Chromatography (HPLC), and potassium was measured using flame photometry.

Main Results:

• Both Hx and potassium levels in vitreous humor increased linearly after death, with rates dependent on temperature.
• Hx levels showed a smaller scatter compared to potassium levels shortly after death.
• The rate of Hx increase per hour was 4.2, 5.1, 6.2, and 8.8 µmol/l at 5°C, 10°C, 15°C, and 23°C, respectively.
• The rate of potassium increase per hour was 0.17, 0.20, 0.25, and 0.30 mmol/l at the same temperatures.

Conclusions:

• Hypoxanthine is a more suitable biomarker than potassium for estimating postmortem intervals, particularly within the first 24 hours and in cases without antemortem hypoxia.
• Increasing postmortem temperature accelerates the Hx and potassium accumulation rates in vitreous humor.