What is rigor mortis?

Rigor mortis is a postmortem phenomenon characterized by the stiffening of muscles after death. This occurs due to biochemical changes in muscle tissue following the cessation of life. When the heart stops beating and oxygen is no longer supplied to the muscles, ATP (adenosine triphosphate), which is essential for muscle relaxation, ceases to be produced. Consequently, the muscles become rigid and remain in that state until decomposition begins, typically starting within a few hours after death and can last for several days before eventually dissipating.

Understanding rigor mortis is important in forensic science, as it can help determine the time of death based on the onset and duration of muscle stiffness. The other options relate to different postmortem processes: the cooling of the body refers to algor mortis, discoloration is often associated with livor mortis, and decomposition involves the breakdown of body tissues, all of which are distinct phenomena occurring after death but do not define rigor mortis.