Blood pH and concentrations of several chemicals are tested in a corpse to help determine the time of death of the victim, also known as the post-mortem interval. These chemicals include lactic acid, hypoxanthine, uric acid, ammonia, NADH and formic acid. 
The decrease in the concentration of oxygen because of the lack of circulation causes a dramatic switch from aerobic to anaerobic metabolism 
This type of analysis can be used to help diagnose various different types of deaths such as: drowning, anaphylactic shock, hypothermia or any deaths related to alcohol or diabetes. Although these types of diagnosis become very difficult because of the changes to the body and biochemical measurements vary after death.