from the Fatalities Investigations Act: http://www.assembly.nl.ca/legislation/sr/statutes/f06-1.htm#5_
5. A person having knowledge of or reason to believe that a person has died under one of the following circumstances shall immediately notify a medical examiner or an investigator:
(a) as a result of violence, accident or suicide;
(b) unexpectedly when the person was in good health;
(c) where the person was not under the care of a physician;
(d) where the cause of death is undetermined; or
(e) as the result of improper or suspected negligent treatment by a person.
See also:
Guidance for doctors completing Medical Certificates of Cause of Death in England and Wales