Gettin' Stiff
Although the development of rigor mortis is highly variable, rigor
is usually well established throughout the body some twelve hours
after death and resolved within thirty hours. It develops in
the smaller muscles of the face and neck first (eyelids, jaws),
spreads to larger muscle groups, and then towards the feet.
Rigor mortis is due to the decomposition of ATP (adenosine
triphosphate), which is required for muscle contraction. When
the ATP is completely gone (about four hours after death), the
muscle becomes regid and remains stiff until actual decomposition
occurs. If there has been violent exertion shortly before
death (i.e., struggle with an attacker, suffocation, drowning,
electrocution), the development or rigor mortis is speeded up
since the ATP resource is already depleted. On the contrary,
is the death is non-violent (carbon monoxide poisoning, etc...),
the process is delayed because ATP reserves are still available.
NOTE: rigor mortis is a poor indicator of time of death since
there are large numbers of variables - activity at time of
death, environmental temperature, and physical characteristics
of the decease. Very obese people may never develop rigor
mortis, while skinny blokes develop it rapidly. Heat speeds
it up, cold retards the process.
back to the body