JMHO, I found this very interesting read :
CAUSE, MECHANISM, AND MANNER OF DEATH
Simply put, the cause of death is the reason the individual died. A heart attack, a gunshot wound, and a skull fracture are causes of death. They are the diseases or injuries that alter the victim's physiology and lead to death.
The mechanism of death is the actual physiological change, or variation in the body's inner workings, that causes the cessation of life.
A shot in the heart, for example, is a cause of death that can lead to one of several mechanisms of death, including exsanguination (bleeding to death) or sepsis (infection that enters the blood stream). Similarly, the victim of a skull fracture can die from direct trauma to the brain (cerebral contusion), bleeding into the brain itself (intracerebral bleed), or bleeding around the brain (subdural or epidural hematoma), all of which can lead to compression of the brain and result in a stoppage of breathing (asphyxia). Again, one cause can lead to death by several mechanisms.
Conversely, one mechanism can result from several different causes. A gunshot wound, stabbing, bleeding ulcer, or a bleeding lung tumor can cause you to bleed to death. In each case, blood loss and shock are the abnormal physiological changes.
For example, say that a man is struck by an intoxicated driver's car and severely injured. The paramedics arrive and transport him to the hospital, where he dies as a result of his injuries. The blunt trauma from the car may have caused lethal brain injuries, and the driver may be charged in the man's death. On the other hand, if the injuries weren't that severe, and the victim died from internal bleeding that paramedical and hospital personnel failed to recognize and treat appropriately, who then is responsible for the man's death? In each of these scenarios the cause of death is blunt trauma from the automobile impact, but the mechanism is either a brain contusion or exsanguination.
http://www.dummies.com/how-to/content/forensics-defining-death.html