Forensic Science
Establishing Time of Death (within the first day)
As a general rule body temperature decreases by 1 1/2 to 2 degree (f) per hour for the first 12 hours, then the temperature slows its cooling down to only 1 degree per hour. The ambient temperature is also taken, in cooler weather or water the temperature decreases rapidly, in warmer weather the body temperature decreases slower. Clothing on the body and any other coverings are also taken into account.
Rigor Mortis
Stiffness of the body known as rigor mortis occurs due to chemical changes in the body. The usually acidic environment of the body becomes alkaline for a brief period of time which causes the muscle stiffness.
The first signs of rigor mortis occurs at approximately 2 hours after death. The first parts to stiffen is the jaw and neck. The rigor travels through the body stiffening the torso, arms, legs and feet - in that order.
Rigor takes up to twelve hours to full develop and may remain active for up to 48 hours before dissipating once more. Again the rigor leaves the body in the same way it appeared - head to toe.
Length of Time since death - after the first 24 hours
The best way to discover the time of death after the first 24 hours is the bacteria cycle and entomology:
Within the first 24 hours flies may lay their eggs in the body's cavities. The eggs hatch (if the weather is correct) within 8 to 14 hours. Knowledge of local insects is neccesary.
2 days after death bacteria will begin to break down the blood causing green staining across the abdominal region.
4 days after death the green staining begins to reach the limbs, bloating of the stomach begins to show.
7 days after death blisters on the body begin to appear and fester.
Hidden Evidence: The Story of Forensic Science... by David Owen, 2000 Burlington Books
Forensic Clues to Murder: Forensic Science in the art of crime detection by Brian Marriner, 1991, Arrow Books
Forty Years of Murder by Prof Keith Simpson, 1978, Grafton Books
Casebook of Forensic DEtection: How Science Solved 100 of the World's Most Baffling Crimes by Colin Evans, 1996, John Wiley and Son's.
Bodies and Crimes by Dr Denis Hocking, 1992 Arrow Books
Justice and Nightmares: Success and Failures of Forensic Science by Malcolm Brown and Paul Wilson, 1992, NSWU Press