But many who knew her didn't believe she'd take her own life, and as the 50th anniversary of her death at age 36 approaches, her tragic end remains shrouded in mystery.
In the new issue of PEOPLE, guest writer J.I. Baker – author of The Empty Glass, a new murder thriller based on her death – uses his research and fresh reporting to explore the truth.
A Mysterious DeathOn August 5, 1962, Monroe was found dead in the bedroom of her Brentwood hacienda.
Toxicology reports showed high levels of Nembutal and chloral hydrate in her bloodstream, and her death was ruled a "probable suicide." But why wasn't her body turned over to medical examiners for more than five hours after it was discovered?
Forensic pathologist Cyril Wecht tells PEOPLE he has "a strong suspicion she might have been injected," given the lack of pill residue found in her stomach – but by whom?
Why did not-yet-tested tissue samples go missing, along with Monroe's phone records? And were Jack and Bobby Kennedy, with whom she was rumored to have had affairs, involved?
For more questions and answers surrounding Monroe's mysterious death, pick up the latest issue of PEOPLE, on newsstands Friday