Dr. Martin MacNeill, a Utah doctor and former Mormon Sunday school teacher, is on trial for the 2007 murder of his wife. Two of his three daughters say that their father “intentionally overdosed” their mother so that he could begin a relationship with his mistress.

"She [Michele MacNeill] means so much to so many people and this is who he took away from everyone, this is our mother," said Alexis Somers, MacNeill’s daughter. "I think he drugged my mother and drowned her. It's been horrifying, and horrifying that we had to wait for this day so long."

MacNeill is charged with first-degree felony murder and obstruction of justice in the death of his wife, Michele. The doctor allegedly encouraged Michele to get a facelift as part of an intricate plan to kill her. After she got the surgery, he reportedly gave her a dangerous combination of Valium, Percocet, and Ambien while she was recovering at home.

When she fell unconscious after taking the drug cocktail, MacNeill undressed Michele, placed her in the bathtub, and pretended to find her there when he called 9-1-1 to report an emergency. According to ABC News, MacNeill hung up on the 9-1-1 dispatcher three times during frantic calls. Prosecutors believe MacNeill hung up that many times in order to delay emergency responders from getting to the scene.

Two weeks after his wife’s death, MacNeill moved nanny Gypsy Willis into the family’s home to care for his daughter, Ada, who was 6 years old at the time. He allegedly began an affair with Willis one year before killing Michele.

Now, six years after Michele’s death, MacNeill’s trial is set to begin. He has maintained his innocence the entire time, despite his children being outspoken about the fact that they believe he killed her.

"It's a whole web of lies. This was very well planned out, and he almost got away with it. And let's hope that the jury convicts my father," said Somers.

Jury selection for the trial will take place on Oct. 15. There are about 120 potential jurors expected to be questioned.