how long before rigor sets in
Rigor Mortis, a stiffening of the muscles, usually starts to take place at around 3 hours after someone is dead with full rigor occurring at about 12 hours after death.After the 12 hour mark the rigor slowly ceases and at around 72 hours rigor disappears.ow long it takes rigor mortis to set in depends on the size of the  dog. The stiffening of the muscles usually begins within three  hours of death and will affect small dog â¦ s much more quickly than  large dogs.