A coroner's or medical examiner's office conducts medicolegal investigations to determine the circumstances under which a person died. These investigations are a scientific inquiry into a death under the coroner’s legal jurisdiction. Each state sets its own standards for the kinds of deaths that require an investigation and report.
The duties of the coroner generally include completing parts of a death certificate, delivering the signed death certificate to the funeral director for filing, assisting state and local registrars by answering inquiries, and delivering a supplementary cause of death report to the State when further investigation or autopsy findings reveal a different cause of death than originally reported. Duties always include determining the time, cause and manner of death. Very few deaths actually require an autopsy to determine the cause. Depending on the jurisdiction, the coroner might also be called a medical examiner.
If a cause of death is not determined within the statutory time frame, a death certificate is filed with the notation "deferred pending further investigation." If death circumstances cannot be confirmed within the statutory time frame due to a suspected accident, suicide or homicide, the manner of death is noted as "pending investigation."
The autopsy and investigation report requirements for each state can be found on the CDC's website.