Suicides are more often determined by cuts than stabs. Usually the body has a huge number of superficial parallel cuts. This shows repeated and hesitant attempts before the person gains success in making a deep final cut. Those cuts are called hesitation wounds and reveal a case of suicide rather than homicide, which typically consists more of a single deep gash. Asphyxiation is also investigated by medical examiners.
Asphyxiation means death from oxygen deprivation in the blood.
An object obstructing the victim's throat or a compression in his chest could also cause asphyxiation. Replacement of oxygen in the red blood cells by another gas, like carbon monoxide poisoning, could also cause asphyxiation. To determine the nature of the incident, certain clues are inspected. Closed garage doors and absence of marks on the body are usually taken as suicide. The presence of tools surrounding the car and grease on the victim's hands point to accidental death.