-Algor Mortis
Investigations can determine how long ago a death occurred by a corpse’s temperature.
Approximately one hour after death, the body cools at a rate of 0.78 degrees Celsius (1.4 degrees farheiet) per hour.
After the first 12 hours, the bod loses about 0.39 degrees Celsius (0.7) per hour until the body reaches the same temperature as the surroundings.
This is just an estimate an will vary depending on surrounding temperatures and conditions.
In cooler environments, the body will lose heat faster than in hotter environments.
If it is windy, heat loss will occur faster.
The surrounding air temperature and other environmental factors are noted when a body is found, because the environment will affect the rate at which the body loses heat.
Excess body fat and clothing will slow heat loss.
Time of death determined by body temperature calculations is always expressed as a range of time because it cannot be calculated exactly.
Good rule of thumb  expect a heat loss of approximately 1 degree F per hour.
-Stomach and Intestinal Contents
From this, it can be concluded;
If undigested stomach contents are present, then death occurred zero to two hours after the last meal.
If the stomach is empty, but food is found in the small intestine, then death occurred at least four to six hours after a meal.
If the small intestine is empty and waste are found in the large intestine, the death probably occurred 12 or more hours after meal.
-Changes of the Eye After Death
In life, the surface of the eye is kept moist by blinking.
Following death, the surface of the eye dries out.
A thin film is observed within two to three hours if the eyes were open at death and within 24 hours if the eyes were covered at death.
Following death, potassium accumulates inside the vitreous humor (fluid of the eye).
Because decomposition progresses at a predictable rate, the buildup of potassium may be used to estimate time of death.
This technique is still being refined and is not yet used as an accurate measure of time of death.
-Stages of Decomposition
A corpse decomposes in predictable ways over time that van help examiners judge when death occurred:
Within two days after death (initial Decay)
Cell autolysis begins following death
Green and purplish staining occurs from blood decomposition
The skin takes on a marbled appearance
The face becomes discolored
After four days (putrefication)
The skin blisters
The abdomen swells with the gas carbon dioxide that is released by bacteria living in the intestines.
Odor of decaying flesh
Within six to ten days
The corpse bloats with carbon dioxide as bacteria continue to feed on tissues.
Eventually, the gas causes the chest and abdominal cavities to burst and collapse.
Fluids begin to leak from the openings as cell membranes rupture.
Eyeballs and other tissues begin to liquefy.
The skin sloughs off
Very strong odor (black putrefication because part of flesh appears black).
Following back putrefication is butyric fermentation  corpse is beginning to dry out, most of the flesh is gone.
Then dry decay  corpse is almost dry am decay is very slow due to lack of moisture.
Decomposition – the process of rotting an breaking down.
Speed of decomposition