The general definition of the term is the study of the process of fossilization and body decay. I have spent multiple weeks down in Knoxville, Tennessee at the University of Tennessee “Body Farm,” a project started by a Dr. William M. Bass in conjunction with several cooperating medical examiners offices. The purpose of the farm is to examine the process of human body decomposition from a forensic investigative point of view. Today there are six such facilities in the United States and they have given forensic investigators, physical anthropologist and medical legal investigators invaluable information concerning the various hallmarks of decomposition including time lines, methods of documentation and the process of recovery for evidentiary purposes. Taphonomy is now one of the major fields of study in death investigation and human identification.
I know this may seem gross but it is necessary to understand artifacts that are postmortem and those that are perimortem. Postmortem refers to that which occurs after death and perimortem refers to that which occurs at or near the time of death. Many new to the field of death investigation will see liquid coming out of the mouth and nose of a decomposing body, and mistake it for perimortem trauma. However, the liquid is the result of a breakdown of tissue, being pushed out of the opening of the body due to the buildup of gasses. Close examination at the lab is the best way to categorize true trauma to the body.