Parents accused of killing their 4-year-old daughter with an overdose of prescription drugs concocted symptoms of mental illnesses to try to have the girl qualify for government benefits, a prosecutor said Tuesday.

Michael and Carolyn Riley were twice rejected for Supplemental Security Income after doctors for the government examined Rebecca and found no indication she suffered bipolar disorder or attention deficit hyperactivity disorder, Assistant District Attorney Frank Middleton said.

The Rileys, of Hull, pleaded not guilty to first-degree murder charges Tuesday in Brockton Superior Court and were ordered to remain held without bail.

The girl was found dead on the floor of her parents' bedroom on Dec. 13. The medical examiner said she died of a lethal combination of prescription drugs, including a fatal dose of Clonidine, which she had been taking for ADHD.

Their attorneys blame the death on her psychiatrist, Dr. Kayoko Kifuji.

Kifuji diagnosed Rebecca with ADHD when she was just 28 months old after her mother said she hits, kicks, spits and was very hyperactive, Middleton said.

Rebecca's older siblings, ages 11 and 6, already had gone to Kifuji and were diagnosed with the same disorders and were receiving Supplemental Security Income, a program administered by the Social Security Administration for disabled children.

Middleton said Michael Riley applied for the benefit for Rebecca after Kifuji diagnosed her with ADHD. Two doctors said she didn't show symptoms and rejected his claim.

Carolyn then took her back to Kifuji and said the girl had "mood swings" and was "driving me crazy," Middleton said. Kifuji then diagnosed her with bipolar disorder at age 3.

Carolyn Riley "continued to feed Dr. Kifuji fabricated symptoms," Middleton said. He said Rebecca's teachers, the school nurse, mental health therapist and neighbors and adults who lived with the Rileys all told the grand jury that "Rebecca showed none of these behaviors."

A second application for benefits was rejected after a doctor said she didn't have signs of the disorder, Middleton said.

The Rileys' lawyers responded with outrage to the allegations of trying to seek financial gain by fabricating illnesses.

"What Mr. Middleton has now raised seems to indicate that a mother who tries to seek Social Security benefits to do the best for her child should be punished," said Michael Bourbeau, Carolyn Riley's lawyer.

"It's Dr. Kifuji who is the cause of any overdose, if that's what it was," said Bourbeau, who said he had not seen the toxicology report.

"The medicines that a totally irresponsible doctor gave her killed her — not the parents," added John Darrell, Michael Riley's lawyer.

Prosecutors say Carolyn Riley got, in one year, more than 200 more pills than should have been prescribed for Rebecca by claiming she either lost or ruined bottles of pills, and telling the pharmacy she had run out.

According to a state police investigator's report, witnesses told police the Rileys gave their daughter large doses of powerful prescription drugs to keep her quiet and sleeping for long periods of time. The couple's other two children had been diagnosed with the same illnesses and were on almost identical prescriptions.

Kifuji agreed to stop practicing medicine until the state Board of Registration in Medicine completes an investigation. Her attorney, J.W. Carney Jr., has said she did nothing wrong and did not overprescribe medication for Rebecca. He declined comment Tuesday.

The Rileys are due back in court April 25 for a pretrial conference.