A coroner is a scientist with a grim specialty: a coroner studies dead bodies and figures out the cause of death.
If you've ever watched a TV show or movie about crime, chances are you've seen a character who was a coroner. If someone dies of a heart attack, there's not much need for a coroner, because everyone knows how they died. When the circumstances are unclear or suspicious, a coroner is needed. Coroners are very helpful in solving crimes.