About.com Chemistry states that rigor mortis can take anywhere between 10 minutes to several hours to set in. Rigor mortis is the time after death when a body begins to stiffen, and the joints lock into place.
About.com Chemistry notes that the time it takes for the onset of rigor mortis to occur depends on the environmental conditions at the time of death, as this affects the temperature of the body. About.com explains that colder temperatures speed up the rigor mortis process. The face is usually the first to set, followed by the body.
Rigor mortis typically lasts up to 72 hours, according to About.com. Afterwards, the joints unlock, and the muscles once again start to relax as a result of the body decaying.