Mary says she’s convinced her sister, Rebecca Zahau, was murdered by her boyfriend’s brother, Adam Shacknai. When Zahau’s body was found by Shacknai hanging from a balcony at his brother’s mansion, the 32-year-old was naked with her hands and feet bound. Mary says her sister would have never taken her own life, especially in this manner.

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The San Diego, CA, Sheriff’s Department determined that Zahau died by suicide, distraught over serious injuries, including brain damage, that her boyfriend’s son suffered while in her care just days prior.

“She was upset about it, but not upset to kill herself,” Mary claims. “The only people that came up with that theory was [Zahau’s boyfriend] Jonah Shacknai and the Sheriff’s Department. They all came to that conclusion that she was upset enough to kill herself, but they had no proof.”

WATCH: What Rebecca Zahau’s Family Claims Happened To Her The Day She Died 

Mary and her family have been fighting for seven years to have her sister’s case re-opened and her death ruled a homicide, so there can be a criminal trial. They hope that with the recent verdict of Adam Shacknai being found civilly liable for Zahau’s death – although he maintains that he is innocent – the Sheriff will consider the new evidence and re-open the case, so they can finally get the justice they say Zahau deserves.

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Hear The 911 Call Made After Rebecca Zahau’s Naked Body Was Found Hanging – And What Her Sister Claims It Proves