HINGHAM, Mass. -- The parents of a 4-year-old girl were facing murder charges Tuesday after the child was found dead from a lethal combination of prescription drugs.

NewsCenter 5's Shiba Russell reported that police have not discussed a possible motive but the pair is expected to appear in Hingham District court Tuesday where prosecutors are expected to lay out their case against the pair.

Caroline Riley, 32, and her husband Michael, 34, have been charged with poisoning their daughter Rebecca, 4, who was found dead on the bedroom floor of their Hull home on Lynn Ave. on Dec. 13, 2006.

"They only lived here for like six weeks and when I first met them, things weren't right," one of the Riley's former neighbors, Phyllis Lipton, said.

Lipton said she remembers the police pulling up to the house on the morning of the girl's death. The medical examiner later ruled that the child died from a lethal combination of prescription drugs.

"Police told me there was a sudden death and I said, 'Oh my God,' and I thought the father had killed the mother," Lipton said.

Authorities said they found amounts of several prescription drugs in the girl's body, including Clonidine, Valproic acid, Dextromethorphan, Seroquel and Chlorpheniramine. Clonidine is prescribed for attention deficit hyperactivity disorder, and Valproic acid and Seroquel for bipolar disorder. Rebecca's death was ruled a homicide resulting from too much Clonidine.

"I was sick for like a month. I could stop thinking about, talking about it. It was overwhelming me. I couldn't even believe I went to work that day because I couldn't believe a little girl died for no reason," Lipton said.

The Boston Globe reported that Michael Riley was not legally allowed in his wife's home the morning of the child's death. The state Depeartment of Social Services had been investigating allegations that he had sexually abused his wife's 13-year-old daughter, who has since been adopted. The couple's two other children remain in foster care.