Livor mortis typically becomes fixed and non-blanching after how many hours following death?

Explanation

## Timing of Livor Mortis Fixation **Key Point:** Livor mortis (postmortem hypostasis) becomes fixed and non-blanching approximately **8–12 hours** after death, though this varies with ambient temperature, body composition, and cause of death. ### Progression Timeline | Time After Death | Appearance | Blanching Response | |---|---|---| | 0–2 hours | Faint, localized reddish discoloration | Fully blanches with pressure | | 2–8 hours | Deepens in colour, spreads | Partially blanches | | 8–12 hours | Dark purple-red, well-demarcated | Non-blanching (fixed) | | > 12 hours | Fixed, may turn greenish (putrefaction) | Permanent | ### Mechanism of Fixation 1. **Early phase (0–8 hours):** Gravity-dependent pooling of deoxygenated blood in dependent tissues; RBCs remain in capillaries but can be mechanically displaced by pressure. 2. **Late phase (8–12 hours onward):** RBCs begin to lyse and haemoglobin diffuses into surrounding tissues; pressure cannot reverse the discoloration. **Clinical Pearl:** In cold environments, fixation may be delayed (up to 24 hours); in warm environments, it may occur within 6–8 hours. **High-Yield:** Blanching livor mortis is a sign of **recent death** (< 8 hours); fixed livor mortis indicates death occurred **> 8–12 hours ago**. This distinction is crucial in forensic time-of-death estimation. **Tip:** Remember: **Blanching = Recent; Fixed = Older.**