Photos from the morgue show the work of a forensic expert trying to determine the time of death from the rigor mortis of a young woman’s corpse.
Rigor mortis, also known as postmortem rigidity, is one of the key indicators used to estimate the time of death. This process begins approximately 2–4 hours after death, as muscles gradually stiffen due to chemical changes in muscle cells, primarily the depletion of adenosine triphosphate (ATP). The body reaches maximum stiffness around 12 hours after death, after which the muscles start to relax over the next 24–48 hours due to enzymatic tissue breakdown.
When determining the time of death, investigators examine which parts of the body are stiff and which remain flexible. Rigor mortis typically progresses from smaller muscle groups, such as those in the face, to larger muscles in the torso and limbs. Experienced forensic experts can assess this progression and use the extent of stiffness to estimate the time elapsed since death.
Temperature plays a significant role in interpreting rigor mortis, as higher temperatures accelerate the process, while lower temperatures slow it down. In practice, the state of rigor mortis is often evaluated alongside body temperature (algor mortis) and postmortem lividity (livor mortis). Combining these methods provides a more accurate estimation of the time of death. Additionally, specific conditions such as physical exertion prior to death, which can speed up rigor mortis, or the presence of certain chemicals, which may alter the process, are also taken into account.
