Parents accused of drugging to death their 4-year-old daughter with an overdose of prescription medication should be tried for first-degree murder, not less-severe charges, the Massachusetts Appeals Court ruled Monday.

In a decision that outlined horrific allegations of neglect and intentional drugging, the appeals court said there was enough evidence to find probable cause that Carolyn and Michael Riley "murdered Rebecca with deliberate premeditation and with extreme atrocity or cruelty."

The decision overturned the ruling of a lower court judge, who reduced the charges to second-degree murder after finding there was no evidence of premeditation.

The Rileys say they were following the orders of Rebecca's psychiatrist, who had diagnosed the girl with bipolar disorder and attention deficit hyperactivity disorder. But prosecutors say the couple kept Rebecca and two older siblings loaded with psychiatric drugs to keep them quiet and to collect Social Security disability payments.

Rebecca Riley was found dead on the floor of her parents' bedroom on Dec. 13, 2006.

A state medical examiner determined that Rebecca died of a lethal combination of prescription drugs. The case reignited a long-running debate within the psychiatric community about whether young children can accurately be diagnosed with bipolar disorder and whether they should be given powerful psychiatric drugs.

The appeals court called the evidence against the Rileys presented to the grand jury "disturbing and graphic."

"Michael, who was abusive, preferred his car to the children," the court said.

The seven-page ruling also outlined evidence that Michael Riley directed his wife to give the children Clonidine, a blood pressure medication sometimes prescribed for attention deficit hyperactivity disorder, "to quiet them down and make them 'pass out"'

"Whenever they began to annoy him, he told Carolyn to shut them up with Clonidine — telling her to 'give them their pills' and 'give them their meds'," the appeals court wrote.

The defense maintains that Rebecca died of pneumonia.

Carolyn Riley's lawyer, Michael Bourbeau, said he was disappointed with the appeals court decision, but will not appeal the ruling to the state's highest court.

"She did not die of a drug overdose, which would make it not a homicide. This is a death by natural causes," Bourbeau said.

Michael Riley's laywer, John Darrell, did not immediately return a call for comment.

A spokeswoman for Plymouth District Attorney Timothy Cruz said prosecutors were reviewing the decision.

Michael Riley is being held without bail and Carolyn Riley was released in November on her own recognizance pending trial. A trial date is expected to be set at a hearing Wednesday.