Death Occurs — The True Concentration Is Fixed and Unknown
At the moment of death, one true blood drug level exists and is never measured directly.
- Unknown: True value (never sampled while alive)
- Lipophilic base: Reference drug (prone to redistribution)
- Estimate: Goal (ante-mortem concentration)
- Site correction: Method (forensic calculator)
Why the target is unknown
Only a postmortem sample can be measured.
The living concentration is gone forever.
Why it matters
Cause-of-death rulings depend on this number.
An uncorrected value can mislead a case.
Every postmortem toxicology result is a proxy, not the truth.
Postmortem Redistribution — Drug Leaves Tissue Reservoirs
After death, drug stored in liver and muscle diffuses passively into central blood.
- Passive diffusion: Driver (no circulation left)
- Liver, muscle: Reservoirs (high drug concentration)
- Tissue → blood: Direction (concentration gradient)
- 0–24+ h: Timescale (PMI dependent)
Reservoir leakage
Cell membranes break down after death.
Stored drug spills into nearby vessels.
Central blood rises fastest
Heart blood sits closest to the liver.
It absorbs the largest diffusion share.
Central blood levels can rise several-fold above the true ante-mortem value.
Sample Site Selected — Where You Draw Changes the Answer
Peripheral, central, and liver samples all report different numbers for one death.
- Most reliable: Peripheral (least redistribution)
- Elevated: Central / cardiac (moderate redistribution)
- Highest: Liver tissue (reservoir itself)
- Femoral draw: Best practice (preferred peripheral site)
Site changes the number
The same body gives three different readings.
Site choice is not a minor detail.
Why peripheral is favored
Distant limb veins see slower diffusion.
They track the true value most closely.
Femoral vein blood is the forensic gold-standard draw site.
Site-Specific Correction Factor Is Applied
A redistribution factor scales the raw number back toward the true value.
- ~1.0×: Peripheral factor (minimal correction)
- up to ~2.6×: Central factor (moderate correction)
- up to ~4.0×: Liver factor (largest correction)
- PMI: Factor grows with (time since death)
The factor formula
Corrected = raw measured ÷ redistribution factor.
Factor rises with site and with time.
Time dependence
Redistribution grows fast, then plateaus.
Most drift happens in the first day.
Longer postmortem intervals demand larger correction factors.
Corrected Concentration Estimate
The calculator returns a defensible estimate of the ante-mortem blood level.
- Corrected value: Output (mg/L estimate)
- Site + PMI: Inputs used (two sliders)
- Case interpretation: Use case (not courtroom proof alone)
- Model estimate: Caveat (confirm with peripheral draw)
Reading the result
The corrected line stays flat across sliders.
Raw values swing; the estimate does not.
Limits of the estimate
Real cases vary by drug and physiology.
Treat the output as a working estimate.
Correction narrows uncertainty — it does not eliminate it.