Livor Mortis · What Is It, Occurrence, and More

Livor mortis begins appearing as dull red patches after 20 to 30 minutes from the time of death. If something presses against the skin, like tight clothing or a hard surface, lividity may be absent in those areas. Over the next 2 to 4 hours, the patches come together to form larger areas of bluish-purple discoloration. At this point, the skin is blanchable, meaning that it can take on a whitish appearance when pressure is applied due to the diversion of blood flow from that region. Blanching can last for up to 8 to12 hours after death. Once pressure is removed, the blood will usually return to the pooled location, appearing bluish-purple in color again. After 12 hours, the skin typically becomes non-blanchable or fixed, meaning applying pressure on the skin during this period will no longer lead to a whitish discoloration.  

Forensic investigators often use these signs to determine the estimated time of death in crime scenes, as well as determining the body position at death. If lividity is inconsistent with how the body was found, it may suggest the body was moved. Assessing livor mortis can also be useful in determining the cause of death, particularly in cases such as hypothermia, carbon monoxide (CO) poisoning, and cyanide intoxication, as such factors can lead to livor mortis taking on a variety of distinguishing colors. For example, CO poisoning produces a cherry-red lividity instead of the usual dark purple. 

Rigor mortis is another post-mortem sign of death and refers to the stiffening of the muscles. Unlike livor mortis, which develops less than an hour from the time of death, rigor mortis begins 2 to 4 hours after death and develops fully by 6 to 12 hours. Stiffening occurs as cells in the body are broken down by digestive enzymes and intracellular calcium is released. This results in continuous muscle contraction since calcium is a necessary component in initiating contraction. Another cause of rigor mortis is the lack of adenosine triphosphate (ATP), or the energy molecules in muscle cells. After death, oxygen is unable to reach muscle fibers, and ATP is no longer produced. This, along with the build-up of lactate and phosphate in muscle tissue, results in an acidic environment that promotes the binding of muscle proteins together. The muscle remains contracted as long as these proteins are bound. Rigor mortis can last anywhere from 1-4 days, after which the muscles become limp again. Lower temperatures speed up the onset of rigor mortis and prolong its duration, whereas warmer temperatures will slow the onset and shorten its duration.  

The remaining two post-mortem signs of death include pallor mortis and algor mortis which both occur shortly after the heart stops beating. Prior to both livor mortis and rigor mortis, the body goes through pallor mortis, or the development of pale skin, and algor mortis, the cooling of the body after the body is no longer producing heat.