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A thorough investigation of a crime scene and an autopsy is needed for a medical examiner to do his job.

Gunpowder residues on the victim's clothing and around his wounds are searched by the medical examiner with regards to cases involving gunshot wounds. These substances can be used to know how far away the gun was when the victim was shot and if it was fired by the victim or by another person.

The medical examiner inspects the victim's body and looks for cuts, stab wounds and defense wounds. A cut is an injury that is much longer than it is deep. Stab wounds are injuries that are deeper than they are long. Defense wounds on the other hand, are cuts caused when the intended victim struggles with an attacker for the knife as a form of self-protection.

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. It may be caused in a number of ways: hanging, which could be an accident or suicide, or strangulation, which is homicide. 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. Finally, a wound caused by a blow in the head or the lack of carbon monoxide in the victim's blood indicates homicide rather than suicide.