Mystery writers often spend as much time researching subjects related to crime as they do writing their stories. One thing they must describe correctly is how a murder victim looks to their sleuth or the police. Was the victim discovered only moments after the murder, or did days or weeks pass before the body was found? Time changes everything when it comes to the appearance of the dead, so mystery writers need to know how long it takes for a human body to decompose.
While cleaning out my research files last week, I came across a piece on this very subject. It was written in 2002 by Jamie Downs, chief medical examiner of the Alabama Department of Forensic Sciences, in reply to a question submitted online by a mystery writer. Downs wrote:
"The rate (of decomposition) depends on the environment and the state of the body at the time of death. As a rule of thumb, a body exposed to open air will decay the same amount in one day as a body in water in one week and a body buried underground in one month. Heat speeds decay; cold slows it down. Rigor mortis (the stiffening of the muscles) and livor mortis (pooling of blood) take place within 12 hours of death. Bacteria in the intestine multiply rapidly as soon as metabolism ceases. Many factors determine how long it takes the body to decompose from there. Is the body in sun or shade? Is it summer or winter? Are there carnivores or insects around? Almost immediately, blowflies can feed on an exposed body and lay eggs in it. Bodies buried deep in the ground are protected from flying insects and warm temperatures, so they tend to decay relatively slowly. A body in a typical casket burial can take decades to decay down to the skeleton if embalmed properly, or as little as a year if not. But such decay can happen in a week if the body is outside, if it is exposed to carnivores, or if it has open wounds. Conversely, bodies can last centuries in a very hot and dry environment, which dries out the body, or in a cold and wet setting, where the body fat turns into a form of soap that acts as a protective covering."
Dr. Downs' explanation of decomposition gives writers a good starting point from which further research may be done if needed.