Which entity assumes custody of a dead body and determines the cause of death when an official investigation is required?

The medical examiner is the entity responsible for determining the cause of death when an official investigation is warranted. This role typically involves cases where the death is sudden, unexplained, or the result of foul play, requiring a thorough examination. Medical examiners are often forensic pathologists and have the expertise necessary to conduct autopsies and analyze other forms of evidence to ascertain how and why a person died.

In contrast, while coroners may also be involved in death investigations, specifically in jurisdictions where they are elected officials with varying levels of medical training, the medical examiner is generally more standardized in their medical qualifications and responsibilities. Funeral directors primarily focus on caring for the deceased and arranging for their burial or cremation, while attending physicians are typically involved in care prior to death and may not be involved in determining cause post-mortem, particularly in cases requiring formal investigation. Thus, the medical examiner holds the specific duty of investigating suspicious or unexplained deaths, making this the correct answer.