As a crime fiction fan, I've always had a fascination with death and forensics though, honestly, I never looked into it very closely. Until now. I'm starting with one article per month because I know that adding more will just make me go crazy. Once a month I'll be doing a mini-lesson in forensics with the intention of informing writers on proper procedure.
As I said before, I am not an expert in this subject so use this as your starting point and please let me know if I do make any glaring errors.
We're starting with body decomposition because it's a fairly common subject in crime fiction (no kidding). This is not including other factors such as frozen, burnt, or drowned bodies - I might cover that one later - this is just a general outline.
A human body decomposes at different rates depending on many environmental factors – temperature, climate, weather, local wildlife, any clothing/coverings etc. – but basically, the body goes through several stages of deterioration.
• At the moment of death the circulatory systems stops (the heart stops pumping blood) and all the skin gets tighter. All the muscles in the body relax and the bowels and bladder empty. Gravity takes over and all the blood begins to pool to the bottom of the body (so if they’re lying on their back, blood will pool on the posterior side of the body – back, buttocks, hamstrings, calves, etc.). After about three hours, rigor mortis has set in, starting at the extremities and small muscles), resulting in stiffness.The skin has turned purple, the eyeballs sinking into the skull. Cells begin to break down and the anaerobic organisms in the digestive tract begin to break down the surrounding tissues – the source of the bad smell. The body temperature also begins to drop from moment of death at a rate of approximately 1.5 degrees per hour. Twelve hours after death, the body is in full rigor.
• After twenty-four hours the body is now the same temperature as the surroundings (ambient temperature). The body will have the smell of rotting meat and the gas causing the smell will begin to build up. The skin can have a marbling effect, turning blue-green colours around the abdomen and neck. Eventually the skin will darken to a near black colour. As the gas continues to swell, bodily fluids will leak from the mouth, nose, vagina and rectum and rigor will begin to fade. After three days the stiffness will be gone from the body. Blowflies are often the first to arrive at the body, usually within two days. The different types of insects found and their stage of maturity can give important clues about the Interval since Death and even if the body has been moved.
• Beginning at four days, the body begins to noticeably decay. This is where bugs and scavengers have usually found the body and the odours become worse. The skin will have blistered and burst open in several places. This is often the point where “neighbours are alerted by the smell” comes in if the body hasn’t been found yet.
• By three weeks the skin, hair and nails are so loose they can easily be removed (slough) from the body which is dehydrated. The soil stains – from the excreted bodily fluids – can actually cause maggots and flies to move away and the vegetation around the body to temporarily die. This can be one of the few indications of a buried body.
• The last stage is the hardest to measure. While many factors can affect this interval , the body is reduced to bones and connective tissue. In a hot climate, it can take just weeks to reach this stage but in a cooler climate it can take months, even years to fully skeletonize a corpse. The state of the bones can be a useful post-mortem interval indicator. Greasy bones are more recent than dry bones. When you are writing about a body that is exposed to the elements in any way, also be aware of the climate you’re writing in.