Livor mortis or postmortem lividity (Latin: livor—bluish color, mortis—of death), one of the signs of death, is a settling of the blood in the lower (dependent) portion of the body, causing a purplish red discoloration of the skin.
Edmond Locard (1877–1966) studied law at the Institute of Legal Medicine and worked subsequently as an assistant to the forensic pioneer Alexandre Lacassagne prior to directing the forensic laboratory in Lyon, France. Locard’s techniques proved useful to the French Secret Service during World War I (1914–1918), when Locard was able to determine where soldiers and prisoners had died by examining the stains on their uniforms.Like Hans Gross and Alphonse Bertillon before him, Locard advocated the application of scientific methods and logic to criminal investigation and identification. Locard’s work formed the basis for what is widely regarded as a cornerstone of the forensic sciences, Locard’s Exchange Principle, which states that

with contact between two items, there will be an exchange. It was Locard’s assertion that when any person comes into contact with…