The mother of the Clueless actress found her dead body on December 20, 2009 and the Los Angeles Coroner originally attributed the death to pneumonia and anemia. Murphy's husband, Simon Monjack, followed her in death five months later from the same causes.
But according to an independent report ordered by her father, Angelo Bertolotti, Murphy did not die from natural causes, leading some to believe that she and her husband may have been poisoned by a third party.
Mr Bertolotti finally secured the release of his daughter's hair, blood and tissue samples for testing after years of litigation and submitted them for independent testing.
The Carlson Company found ten heavy metals in Brittany's system which were several times higher than World Health Organization high levels at the time of her death.
'If we were to eliminate the possibility of a simultaneous accidental heavy metals exposure to the sample donor then the only logical explanation would be an exposure to these metals (toxins) administered by a third party perpetrator with likely criminal intent,' the report says.
Heavy metals are found in most rodenticides and insecticides meaning the actress could have been slipped rat poisoning or bug killer.
At the time of her death, Brittany displayed all the symptoms of heavy metal poisoning including: headaches, dizziness, abdominal cramps, coughing, sweating, disorientation, wheezing, congestion and pneumonia.
Murphy's husband also exhibited similar symptoms before his death, leading some to believe he too was poisoned. Mother-in-law Sharon discovered his body as well after moving in with him following her daughter's death.
'Vicious rumors, spread by tabloids, unfairly smeared Brittany's reputation,' Mr Bertolotti told the Examiner. 'My daughter was neither anorexic nor a drug junkie, as they repeatedly implied. Brittany and Simon were ridiculed by The Hollywood Reporter, when they complained of being under surveillance in fear for their lives. I will not rest until the truth about these tragic events is told. There will be justice for Brittany.'
At the time of her death, early speculation was that the actress died of a drug overdose or anorexia after years of shocking weight loss.
Prescription pills were found in the actress' system, but they were treating a cold and respiratory infection.
Murphy was perhaps most famous for her role in 1995's Clueless, but she also had more serious roles in Girl, Interrupted and played Eminem's love interest in 8 Mile - the movie about the rapper's life.
At the time of her death, Murphy's career had tapered off and her last major role was in 2004's Little Black Book.
Before marrying Monjack, Murphy dated Ashton Kutcher, her co-star in the film Just Married. After breaking up with the actor, she went on to have two serious relationships that led to engagements with talent manager Jeff Kwantinetz and production assistant Joe Macaluso before marrying Monjack, a screenwriter, in May 2007.
