Until recently, decay odor has not been used as a forensic investigative tool beyond body reconnaissance by cadaver dogs. The research presented in this study is attempting to broaden the value of decay odor through evaluating it as a time since death indicator. Decomposition is the result of two internal processes, autolysis and putrefaction, and many external factors, i.e., bacteria, carnivores, insects. Autolysis is the breakdown to cells following circulatory stasis. Putrefaction is the destruction of the organism through bacterial activity. Some of the byproducts of putrefaction are odiferous compound such as cadaverine, putrescine, volatile fatty acids (VFA\u27s), methane and hydrogen sulfide, which produce the decay odor. As decomposition progresses the concentration of various by-products that contribute to the decay odor are expected to vary in a predictable pattern that correlates to temperature. To test this hypothesis the odors of several decaying corpses were collected and analyzed using electronic nose technology.
The greatest obstacle to successfully studying decay odor was the collection of a representative and replicable sample. A portable sampling device was designed to collect an appropriate sample. The device consisted of connecting three glass pipettes filled with molecular sieve to the inflow nozzle of an air pump. Molecular sieve, a universal dryant, was capable of capturing the odor causing agents under field conditions and releasing the same agents under the analytical conditions of the electronic nose in the laboratory. Collecting three samples simultaneously, per the three pipettes, minimized the intersample error and reduced the sampling time.
Aroma samples were collected from eleven decaying individuals at regular intervals. The human subjects were donated for scientific study and met several criteria: 1) known time of death, 2) known cause of death, 3) received during the fresh stage of decomposition, and 4) unautopsied. Included in the study were eight males and three females. All individuals were white, non-Hispanic. Age range was from 25 to 98 years. Cause of death was natural in all case but three, two suspected drug overdose and one suicide by hanging. Ten corpses were enclosed in a body bag during the decomposition process to concentrate and isolate the odor. One corpse was not placed in a body bag. A small hole was cut in each body bag through which the sample was taken. At each sampling event the temperature and humidity, as well as the intersample high and low temperature and humidity and rainfall, were recorded. The fluctuation and accumulated effects of temperature was summarized as accumulated degree days (ADD). Control samples were collected by sampling air contained within empty body bags. Four of the ten body bags were disturbed by carnivore activity during the decay process.
The results of the study show that the aroma pattern as detected by the electronic nose did not change over time. However, the concentration of the odor did change. The intensity of the odor positively correlated to ADD when the body was isolated in an undisturbed body bag. Intensity of the odor did not correlate to ADD when the body bag was disturbed or the body was not placed in a body bag. At this time, odor as a time since death indicator is only applicable to a sample collected from bodies isolated in body bags. In order to expand the applicability of this method the sensitivity of the sampling method must be improved. Furthermore, important odor pattern variation may become detectable with increased sensor sensitivity of the electronic nose. In sum, the concentration of odor positively correlated to ADD when specific conditions are met. However, aroma pattern change is undetectable
