Mary says that since her sister, Rebecca Zahau, died on July 13, 2011, she has vowed to get justice for her. She claims that the 32-year-old, who was found gagged and hanging naked with her hands and feet bound, was murdered by her wealthy boyfriend’s brother, Adam Shacknai. Police, however, claim the young woman died by suicide, distraught over serious injuries, including brain damage, that her boyfriend’s son suffered while in her care just days prior.

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“I believe that Adam Shacknai murdered my sister,” Mary says. “My family and I have been fighting every day for the last seven years to try to bring Adam Shacknai to court … Fighting Adam Shacknai and his team of attorneys was like David fighting Goliath.”

Mary says that after appearing on Dr. Phil and having a second autopsy done on her sister’s body, she and her family believed they had enough evidence to win a civil trial against Adam.

WATCH: Rebecca Zahau’s Family Shares Details From The Trial For The First Time Since Adam Shacknai Found Responsible For Her Death

In the video above, Mary describes what it was like going through the trial. And, see footage from inside the courtroom, including the verdict against Adam being announced. In an exclusive interview on Tuesday’s episode of Dr. Phil, Mary, her husband, and their attorney share details from the civil trial for the first time since Shacknai was found responsible for Zahau’s death. Check here to see where you can watch.

Adam Shacknai maintains that he is innocent of any wrongdoing and did not kill Rebecca Zahau.

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