At what time interval after death does rigor mortis typically become fully established in the body?

Explanation

## Timeline of Rigor Mortis Development **Key Point:** Rigor mortis is a post-mortem stiffening of muscles due to depletion of ATP and cross-linking of actin and myosin filaments. The onset and progression follow a predictable sequence. ### Phases of Rigor Mortis | Phase | Timeline | Characteristics | |-------|----------|------------------| | Onset | 2–4 hours | Begins in small muscles (eyelids, jaw, neck) | | Progression | 6–12 hours | Spreads to trunk and limbs; advancing stiffness | | Full Establishment | 12–18 hours | Maximum rigidity achieved throughout the body | | Resolution | 24–48 hours | Begins to disappear due to putrefaction and autolysis | **High-Yield:** Full establishment of rigor mortis occurs at **12–18 hours** post-mortem, which falls within the **18–24 hour** window as the period when rigor is fully established and at its peak. This is the most commonly tested timeframe in NEET PG and is consistent with standard forensic medicine texts (Parikh's Textbook of Medical Jurisprudence and Toxicology; Modi's Medical Jurisprudence). **Clinical Pearl:** The progression follows a cephalocaudal (head-to-toe) pattern. Rigor begins in the small muscles of the face (eyelids, jaw) at 2–4 hours, spreads to the neck and upper limbs by 6–12 hours, and is fully established throughout the entire body — including the lower limbs — by approximately 12–18 hours. The 18–24 hour window represents the period of complete, peak rigidity. **Warning:** Do not confuse the *onset* (2–4 hours) with *full establishment* (~12–18 hours, i.e., within the 18–24 hour range). Option A (6–12 hours) describes the phase of active spread/progression, not full establishment. Exam questions frequently test this distinction. ### Factors Affecting Rigor Mortis Timeline - **Accelerated onset:** High ambient temperature, muscular exertion before death, electrocution, tetanus - **Delayed onset:** Low ambient temperature, prolonged illness, cachexia - **Absent rigor:** Severe decomposition, putrefaction, certain bacterial infections **Reference:** Parikh's Textbook of Medical Jurisprudence, Forensic Medicine and Toxicology, 6th edition; Modi's Medical Jurisprudence and Toxicology.