Apr
And if it is, is it possible for them to miss something, like cancer if they find state for example, poison or pills in ones digestive system? Also, is it possible for the coroner to be negligent and only report one cause of death, (even if there were multiple?) I'm asking for a book I'm writing, thank you. 
Answer:
Yes, in most places it's mandatory to perform an autopsy after a suicide to rule out other causes of death, such as homicide. I took a class on the psychology of death and dying and our local coroner (with the sheriff's office) talked a lot about suicide death because that’s so common these days. In most cities, autopsies are not done very well and are not very careful. It would be easy for them to overlook an illness and most autopsies don’t look for an illness if they already have another cause of death that they suspect (such as suicide). As soon as they find the evidence they expect to find, they usually don't care what else is there. Regardless, the family will probably never know the results of the autopsy except for the cause of death on the death certificate. Some counties do have exceptional coroner's, and this really depends on the budgeting and priorities of the sheriff office. If they want to solve crimes and detect crimes, they’ll have a good budget for this department and will pay for great autopsies. Most places spend their money on preventing death rather than solving crimes.
Answer:
I assume you are trying for as much accuracy as you can get - first, it would depend on what state the person lived in (or country). In some says autopsies are required for any death by violent means. I would assume that if the cause of death was obviously self-inflicted then the coroner or medical examiner might not do an in-depth autopsy unless he suspected that the death could be from another cause.
If you want your character to discover the reason for the suicide gradually, it might help you to reach that if, for example, the suicide happened when the daughter was very young and she was told only that it was suicide and not that the mother had a terminal illness, or perhaps the mom had contracted AIDS and the family was too humiliated by that fact that all the daughter was told was her mom committed suicide.
As the writer you’ve a lot of leeway. As to the question about what the coroner might or might not reveal, it would help if you could interview someone in that field.
Writer's Digest books have a lot of books written as resources for writers that cover everything from forensics to weapons. You might look into seeing what they might have. Your local library might have some of their books but a lot of those books disappear from libraries.
Your doctor or the local police could advise you about the laws regarding autopsies.
Good Luck!
Answer:
Have you been reading Agatha Christie? Good for you! Autopsy exams are required on any murder or suicide, as well as for an unattended death which means a death where a doctor has NOT been caring for someone.Attended death is like if someone did have cancer or a bad heart condition and had a doctor. If you had a poor unqualified doctor in attendance, of course the real cause of death could be missed. Watch NCIS as they're pretty good showing an autopsy there.After the physical part is done they test for drugs to see if there are overdoses or poisonings present. With your idea, the mom could have killed herself, but had a disease she didn't want anyone to know about (maybe leprosy or syphilis?).Good luck.Write on!