Post-Mortem Interval (PMI) Calculation
Arpad A. Vass, Ph.D., The Elusive Universal Post-Mortem Interval Formula, Forensic Science Int. 204 (2011) 34-40Formula requirement checklist (please refer to reference for additional details and explanation):
- Corpse must be at least one day old
- Corpse should be fairly intact
- Temperature must be above 0° C | 32° F
- aerobic decomposition (Ex. decedent on surface, loosely clothed, under loose debris, etc.)
- anaerobic decomposition (Ex. decedent buried, tightly wrapped, sealed in containers, etc.)
- Temperature is considered 'Warm' if above 12° C | 53.6° F
- Temperature is considered 'Cold' if below 12° C | 53.6° F
Estimating % total body soft tissue decomposition based on temperature and decompositional stage:
1. Determine death scene temperature and moisture
2. Select a Decompositional stage
3. Estimate the % total body soft tissue decomposition from the provided range
- Fresh stage (Warm 1-10% | Cold 1-20%) Color changes occur ~5%; Skin surface appears wet ~10-15%
- Bloat stage (Warm 11-35% | Cold 21-45%) Skin slippage starts ~15% with maximum ~30%
- Decay stage (Warm 36-85% | Cold 46-85%) Abdominal purge ~35-40%, abdominal collapse ~50%
- Mostly skeletonized stage (86-100%) Bone exposure [hands/feet ~60%; arms/legs ~70%; torso ~85%]
NOTE: This calculated value is intended to provide law enforcement with an easily obtainable, rapid and fairly accurate PMI estimate while waiting for the detailed laboratory analysis of evidence collected at the site of discovery, which will provide the PMI range to be used in any future legal proceedings.
The calculated value is a maximum time if:
Total body soft tissue decomposition is < 100% and any remaining tissue is soft and pliable.
The calculated value is a minimum time if: Total body soft tissue decomposition is = 100% or if any remaining tissue is hard and non-pliable (mummified).