BURLINGTON — A day-care operator charged with killing an infant she was baby-sitting two years ago told reporters Wednesday that there is no justification for the continued prosecution of her case, given new questions about the child’s cause of death.

“I’m still hurting and grieving over the death of Ridhima, who I dearly loved,’’ Pallavi Macharla, 41, said quietly in brief remarks, flanked by her lawyer and her husband. “I didn’t do anything to hurt the baby, in any way.’’

Her comments came a day after new developments about her prosecution were made public: A medical examiner in the case, Dr. Anna McDonald, last month revised the child’s cause of death from shaken-baby syndrome to unexplained cardiac arrest, a change she made after reviewing new defense medical reports.

Despite McDonald’s new finding, Middlesex District Attorney Marian Ryan announced that she was not dropping murder charges, largely because the state’s chief medical examiner, Dr. Henry Nields, who supervised McDonald during the autopsy, maintains that 6-month-old Ridhima Dhekane was killed and is not revising the death certificate. McDonald left the medical examiner’s office within months of Ridhima’s death in March 2014 and is now on the faculty at Wake Forest School of Medicine in North Carolina.

This case marks the third time in two years that a medical examiner has backed off a finding that a child died of shaken-baby syndrome in Middlesex County. In the two other cases, Ryan dropped the charges. One case involved an MIT employee, Geoffrey Wilson, accused of killing his infant son, and the other involved an Irish nanny, Aisling Brady McCarthy, charged with murdering a Cambridge baby in her care.

Macharla’s lawyer, J.W. Carney Jr., insisted that the prosecution in this case is now doomed as well, even if both pathologists testify. He said a jury cannot find guilt beyond a reasonable doubt, given such mixed testimony.

“It should end now,’’ he said.

But Ryan said that a conviction is still possible, once a jury reviews all the evidence, including the extent of the child’s brain injuries and spinal fractures, and the fact that Macharla did not call 911 right away when she noticed the baby was unresponsive. She also said there is no evidence the child’s heart was faulty, given that the organ has been transplanted into a new child who is thriving.

Some defense lawyers predicted that prosecutors face an uphill battle, saying it is highly unusual for jurors to hear from two pathologists representing the state, one calling it a homicide, another saying it was a rare and tragic cardiac event.

“This is going to cast a serious cloud on the prosecution,’’ said John Amabile, a veteran defense lawyer from Brockton.

Several top child abuse specialists, however, said the totality of the evidence in the case appears to be strong and called for an investigation into the medical examiner’s office, given the mixed messages emerging on shaken-baby cases.

“It’s a huge concern to the child abuse community,’’ said Dr. Stephen Boos, who chairs the child abuse and neglect committee of the Massachusetts chapter of the American Academy of Pediatrics.

Boos said he is particularly struck by how these medical examiners appear to be backing away from homicide rulings after being exposed to defense witness reports.

In McDonald’s case, she reviewed the case for a year before concluding it was a homicide, then twice modified her findings, including her final conclusion that the baby died of cardiac arrest. This finding mirrors what one of the top defense experts had concluded.

Boos also noted that McDonald’s homicide findings and subsequent retractions took place while she was no longer working for the state.

“You take a year to make a determination and then you make these changes,’’ Boos said. “It’s dramatic. It’s remarkable.’’

A spokesman for the state medical examiner’s office did not respond to the Globe’s efforts to learn more about why a former state examiner continues to evaluate a case.

Former attorney general Martha Coakley, who worked extensively on child abuse issues when she was Middlesex district attorney, said she cannot remember an instance of a medical examiner reversing an opinion on a shaken-baby case. She also said the medical examiner’s office deserves serious scrutiny.

She said she hopes defense medical reports are not getting outsize importance in the minds of medical examiners.

“We need to distinguish between real evidence and defense theories that are trying to create reasonable doubt,’’ she said.

Carney said Wednesday that the case is like so many others across the country where doctors and law enforcement falsely accuse someone of killing an infant. He said new scientific developments have “completely debunked the theory’’ of shaken-baby syndrome.

Patricia Wen can be reached at wen@globe.com. Follow her on Twitter at @GlobePatty.