Per this /r/legaladvice thread:
I was under the impression that a coroner's primary function was assisting law enforcement on the scene of an unattended death or homicide. It was very surprising for me to learn that in Louisiana, the coroner is also the only person with the authority to involuntarily commit someone.
Unlike other states, Louisiana requires/attempts to require the county coroner to be a practicing physician:
The candidate shall be a licensed physician, unless no licensed physician in the parish will accept the office. The coroner shall be a resident of the parish, or a licensed physician who is not a resident of the parish but maintains a full-time medical practice at a principal medical office facility in the parish
Simply put, the coroner is the only elected position that would by default have the expertise needed to make a medical decision that denies someone their freedom and does not need a trial or any of the other criminal justice safeguards.
Side note: The "unless no licensed physician..." part of the law had controversy in modern times(<20 years) because of this privilege.
We have parishes, not county’s! And I’m not sure, the south is weird.