## Livor Mortis (Post-mortem Hypostasis) — Timeline and Fixation **Key Point:** Livor mortis is the purple-red discoloration of dependent parts of the body due to gravitational settling of red blood cells and haemoglobin deoxygenation after circulation ceases. ### Stages of Livor Mortis Development | Stage | Time Interval | Characteristics | |-------|---------------|------------------| | **Appearance** | 30 minutes – 2 hours | Faint purple-red patches appear in dependent areas | | **Blanching phase** | 2–8 hours | Discoloration is visible but blanches on pressure (RBCs not yet fixed) | | **Fixation begins** | 8–12 hours | Discoloration becomes darker and begins to lose blanching ability | | **Complete fixation** | 12–24 hours | Fully fixed, non-blanching; RBCs have haemolysed and stained tissues | **High-Yield:** The transition from **blanching to non-blanching (fixed) livor** occurs at **8–12 hours**, making this the critical forensic timeframe. After fixation, livor no longer blanches on pressure. ### Mechanism of Fixation 1. Red blood cells settle in capillaries of dependent areas (gravity) 2. Haemoglobin is deoxygenated → purple-red colour 3. Cell membranes rupture (autolysis) → haemoglobin leaks into tissue 4. Haemoglobin binds to tissue proteins → **fixed, permanent staining** **Clinical Pearl:** A blanching livor mortis at autopsy suggests death occurred within the last few hours; a fixed, non-blanching livor suggests death occurred at least 8–12 hours prior. **Mnemonic:** **LIVOR** = **L**ate (8–12 hrs for fixation), **I**rreversible (once fixed), **V**iolet-red, **O**f dependent areas, **R**ed blood cells settled.
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