What does a forensic investigator do?

A Forensic Investigator could be someone who works aside with a Medical Examiner from start to finish or a particular case. Such as securing evidence from a crime scene where someone has died from unnatural causes. Unnatural death's are as follows:

Homicide, Suicide, someone found unresponsive, Children with no apparent health issues,Car Accident, drowning, any act of terrorism, depending on the State but death within 24 hours of admission in a hospital, Nursing facility for care. Basically anything out of the ordinary. Also a Forensic Investigator would assist in the Autopsy, taking tissues for the lab, X-ray a decedent for foreign matter to recover. The core mission is to determine cause and manner of death after the investigation is completed.