[Cadaver lipid: various origins add to the difficulty of assessing postmortem time]

Establishing the length of time since death is particularly difficult in corpses showing advanced putrefaction. One particular sign of advanced decay is the formation of adipocere, as observed mainly in drowned bodies or following a long period of storage under airtight conditions. During storage in an open, damp environment (e.g. water) the formation of adiopocere becomes visible after approximately 3-6 months and can be found in more extensive form after approximately one year. In this state bodies show evidence of a partly waxlike and partly pasty condition. Continued storage ultimately results, among other things, in further decomposition due to the action of microorganisms from the surrounding area-even if this is chronologically delayed. An exception is provided by the formation of adipocere under air-tight conditions (e.g. wrapped in plastic material or in mass graves). Initially autolysis and heterolysis also occur, involving the release of fatty acids from the lipids produced naturally in the body. As a result of the subsequent hydrogenation of the fats by the action of bacterial enzymes, the unsaturated fatty acids are partially converted into saturated fatty acids. As the fatty acids released in large quantities during adipocere formation clearly have a bactericidal effect, further bacterial decomposition is stopped at this early adipocere stage. Additional microorganisms from outside can no longer infiltrate when this hermetic seal is in place. In addition, the lack of calcium (e.g. from water or moist earth) can be a reason for the fact that further adipocere development, leading to wax-like hardening of the fat, is arrested. The soft parts of the body retain a soft, viscous consistency. Thus the condition of the body can remain constantly preserved over many years and no longer allows a reliable estimate to be made of the period of time since death.