In most developed countries, there is a mechanism in place to determine cause of death and nothing is ruled out until eliminated.
A medical examiner's duties may vary depending on location. Typically, a medical examiner's duties may include:
investigating human organs like the stomach, liver, brain,
determining cause of death,
issuing death certificates,
maintaining death records,
responding to deaths in mass disasters,
identifying unknown dead, or
performing other functions depending on local law.
In some jurisdictions, a coroner performs these and other duties. Within the United States, there is a mixture of coroner and medical examiner systems, and in some states, dual systems. The requirements to hold office vary widely between jurisdictions.