Artefacts due to putrefactive gas production - an overview.

Autolytic and putrefactive processes can cause considerable alterations to soft tissues and internal organs that may complicate forensic assessments. An overview was undertaken of the range of taphonomonic changes and processes that may result from postmortem putrefactive gas accumulation. The most commonly encountered phenomenon was purging of putrefactive fluids from the nose and mouth that was on occasion confused with bleeding from antemortem trauma. Much less common was putrefactive 'rigor mortis' where the limbs extend due to the accumulation of soft tissue and subcutaneous gas. This may sometimes be associated with alteration of the position of a body suggesting that it had been deliberately moved. Distension and stretching of the skin and subcutaneous tissues may cause recently sutured surgical incisions to dehisce, raising the possibility of inflicted incised wounds. Raised intra-abdominal pressures may cause diaphragmatic herniation of small intestine and has been associated with so-called 'coffin birth' where a fetus is expelled from the uterus after death due to pressure on the fundus. Gas accumulation on postmortem computed tomography examination may be confused with air embolism or the effects of trauma. All of these changes are the result of anaerobic bacterial action generating gases such as methane, carbon dioxide and hydrogen sulphide resulting in pressure gradients.