BROCKTON, Mass. — A man accused along with his wife of giving their 4-year-old daughter a lethal prescription drug overdose to keep her quiet was convicted of first-degree murder Friday.

Michael Riley, 37, was found guilty in the December 2006 death of daughter Rebecca. The jury had begun deliberating his case Thursday afternoon. He faces an automatic sentence of life in prison without parole.

Additional Photos

Michael Riley, left, is consoled by his attorney John Darrell on Friday in Brockton, Mass., after he was found guilty of first-degree murder in the prescription drug overdose of his daughter Rebecca in December 2006. The Associated Press

His wife, Carolyn, was convicted of second-degree murder last month. Her mandatory life sentence allows for parole after 15 years.

“It’s a very difficult decision. I’m going to look at it and file an appeal,” defense attorney John Darrell said.

The Rileys were accused of giving their daughter a fatal overdose of Clonidine, which she was taking for attention-deficit hyperactivity and bipolar disorders. Defense attorneys said Rebecca died of pneumonia and blamed the overdose on lax monitoring by a psychiatrist who had prescribed the medication.

Assistant District Attorney Frank Middleton told the jurors in closing arguments that Michael Riley either gave Rebecca the extra pills himself or told his wife to do so.

“He knows it’s going to shut her up, and shut her up for good,” Middleton said.

Middleton said Riley was a cold-hearted father who made up symptoms of mental illness in Rebecca and his two other children so he could collect Social Security disability benefits for them. The defense said Riley was trying to take care of his family while struggling with problems of his own, including bipolar disorder.

Riley repeatedly ordered his wife to increase Rebecca’s dose of Clonidine, the prosecutor said, to keep her quiet and out of his way. The night she died, she was given two to three times her daily dose, Middleton said.

A state medical examiner found that Rebecca died of the combined effects of Clonidine; Depakote, an anti-seizure and mood-stabilizing drug prescribed for bipolar disorder; and two over-the-counter drugs, a cough suppressant and an antihistamine. The amount of Clonidine alone in Rebecca’s system was enough to be fatal, the medical examiner said.

Defense attorney Darrell said his client had little to do with Rebecca’s medication because he had been living apart from the family for months and returned about a week before she died.

Darrell blamed Rebecca’s death on her psychiatrist, Dr. Kayoko Kifuji, who diagnosed Rebecca with ADHD and bipolar disorder by the time she was 3. Darrell called Kifuji “the most irresponsible doctor you may have ever heard of in your life,” said she did not adequately monitor the child and said she repeatedly increased the Clonidine dosage after Carolyn Riley had done so on her own.

A grand jury refused to indict Kifuji in Rebecca’s death. In September, she was reinstated to her job as a child psychiatrist at Tufts Medical Center in Boston. The hospital said it conducted a complete review with independent experts and concluded that Kifuji’s care was appropriate and was not the cause of Rebecca’s death.

Still, Plymouth District Attorney Timothy J. Cruz said after the verdict that prosecutors will ask the Board of Registration to review the decision to allow Kifuji to continue to practice medicine in Massachusetts.

Prosecutors will send a package to the board – including information extrapolated during the trial and what investigators gathered as they probed the case – to support their request for the review, Cruz said.

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