CASE STUDY: Decomposition of a Human Body

Source:

"Insect Activity and its Relationship to Decay Rates of Human Cadavers in East Tennessee", William Rodriquez and William Bass, Journal of Forensic Sciences, JFSCA, Vol. 28, No. 2, April 1983, pp. 423-432.

Background:

A decomposing corpse, which has been discovered lying in a wooded area, secluded lot, or in an open field, presents the forensic scientist with many questions to be answered. One of the most important questions is the "time interval since death." The answer to this question is, in many cases, crucial to establishing the identity of the individual. Forensic scientists faced with this question must rely on their experience of previously known cases. These results in a rough estimation of time since death, based on nonspecific criteria.

In this case study, you are tasked to build a simulation to measure time needed for a human cadaver of some total body weight to decompose down to skeleton. Model building specifics are described below.

Building the Model:

A human cadaver lying in a field (or buried some depth) can undergo only one process: decay. Decay of the body is a time-dependent phenomenon that depends directly on three processes:

Decay by insects, primarily maggots
Depth of the burial in the ground (assuming no casket or other external protective objects)
Number of carnivores active in the area.

Decay by insects is determined by five factors:

Trauma to the body (open wounds, etc.)
Temperature
Humidity
Rainfall
Amount of clothing on body

Each of the factors has a certain "weight"; that is, some factors influence decay more than others. These weights are shown as an activity: that is, an input graph for each factor of the actual quantity and its subsequent influence on the decay process must be utilized. The graph below shows the relationship between number of carnivores (0 to 100) and the carnivore activity decay factor (listed as "activity" on the y axis). Thus, if there are 50 carnivores, the activity level that influence decay is about 0.005 (times the total body weight)

Each of the other factors is shown below with their corresponding graphs. You will need to create each of these input graphs using the appropriate skills.

The total decay for the body is simply a summation of the three main factors (insects, burial depth, and carnivores) times the total body weight. The total decay by insects is simply a summation of the five factors that influence insect activity.

For your model, you might wish to try these settings, then investigate your own settings:

Total body weight: 150 lbs.

Burial depth: 2 feet

Carnivores: 25

Clothing: 60 percent

Humidity: 65 percent

Rainfall: 2 inches

Temperature: 15 degrees Celsius

Trauma to the body: 50 percent (pretty beat-up!)

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