Cadaveric spasm, also known as instantaneous rigor, cataleptic rigidity, or instantaneous rigidity, is a rare form of muscular stiffening that occurs at the moment of death, persists into the period of rigor mortis[1] and can be mistaken for rigor mortis. The cause is unknown, but is usually associated with violent deaths happening under extremely physical circumstances with intense emotion.[2] Cadaveric spasm may affect all muscles in the body, but typically only groups, such as the forearms, or hands. Cadaveric spasm is seen in cases of drowning victims when grass, weeds, roots or other materials are clutched, and provides proof of life at the time of entry into the water. Cadaveric spasm often crystallizes the last activity one did prior to death and is therefore significant in forensic investigations, e.g. holding onto a knife tightly.
Jayawardena, Hemamal, Forensic Medicine and Medical Law, 2 Eds (2004), Siddhartha Press, Colombo Sri Lanka.