Rigor mortis

•      It is the muscular (smooth, skeletal and cardiac) stiffening of the body following death.

•      When an animal dies, muscles are initially flaccid, then they stiffen and they become flaccid again.

•      When an animal dies, muscles are initially flaccid, then they stiffen and they become flaccid again.

•      Rigor sets first in smaller muscle groups and joints, usually the muscles of head and then moves to larger muscle groups.

•      It dissipates in the same order.

•      Rigor can be forcibly broken with manipulation and will not recur unless it is broken before full development.

•      It starts 1-8 hours and ends 20-36 hours after death.

•      When an animal dies, muscles are initially flaccid, then they stiffen and they become flaccid again.

•      After death, absence of blood supply causes anaerobic condition in sarcoplasm of muscle fibers. Lactic acid is produced through anaerobic glycolytic pathway causing muscle fibers to contract and shorten.  That leads to stiffness of muscle and immobilization of joints.

Time of death estimates in aniamls

Feelings	Time of Death
Warm and flaccid	< 3 hours
Warm and stiff	3-8 hours
Cool and stiff	8-36 hours
Cool and flaccid	>36 hours