Logan Muir, of King's High School, asks :-

How long does it take for a human body to decompose?

Arpad Vass, a forensic biochemist at Oak Ridge National Laboratory, USA, and who studies the biochemical changes in order to date the time of death of a corpse, responded.

The length of time someone takes to decompose is a complicated process, but is primarily dependant on temperature. In our studies we have worked out a simple formula, which describes the soft tissue decomposition process for persons lying on the ground. The formula is y = 1285/x (where y = the number of days it takes to become skeletonized and x = average temperature in Centigrade during the decomposition process). So, if the average temperature is 10C, then 1285/10 =128.5 days for someone to become skeletonized.

Of course this is a rough estimate since many factors affect this rate. Buried individuals and ones submerged in water have different rates of decomposition. Injuries affect the rate as well since damage to the skin increases blood loss, insect and bacterial action.

In severe environments such as in the arctic or in deserts, desiccation occurs and this makes any accurate determination extremely difficult. Carnivore activity is yet another factor which can radically affect decomposition. Exclusion of insects and carnivores will slow down the process, whereas exposure to many (or larger) carnivores will increase the rate.

Remember that decomposition does not end after the soft tissue has disappeared. The skeleton also has a decompositional rate that is based on the loss of organic (collagen) and inorganic components. Some of the inorganic compounds we study to determine how long someone has been dead include calcium, potassium and magnesium. As with soft tissue, these leach out of bone at a rate determined primarily by temperature and exposure to moisture.