CHICAGO (CBS) — After “48 Hours” uncovered evidence that casts doubt on the verdict that sent a teacher to prison for the death of a 16-month-old boy, the Lake County Coroner was calling for authorities to reopen the case.

“If you’re going to put somebody in jail for murder, you’d better be absolutely certain of your findings,” the coroner, Dr. Thomas Rudd said Tuesday.

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Rudd called the 2011 conviction of Melissa Calusinski, now 27, a miscarriage of justice. He said microscopic evidence showed Benjamin Kingan suffered a head injury.

“No question about it. This needs to be reexamined. This case needs to be reopened. We need to find out what happened to that child,” he said.

His examination of the evidence found Kingan died of a massive head injury suffered weeks before he died.

Rudd, who was elected as Lake County Coroner in 2012, told “48 Hours” he couldn’t believe what he saw after he took a look at the autopsy evidence four years after Calusinski’s conviction. He said it’s obvious the brain injury he suffered was old – one that had been healing for two to three months. He said a minor injury on the day Kingan died exacerbated the old injury, and shut down Kingan’s breathing system.

“The child had an old injury. The body was trying to respond by reabsorbing the blood. Now this child was known to be a head banger, so he kept hitting his head, and most likely kept re-bleeding,” Rudd said.

Forensic pathologist Eupil Choi has admitted his trial testimony was mistaken, and he overlooked the earlier injury, but has said he wouldn’t change his mind that Kingan died from a severe head injury caused on the day he died.

“He’s wrong on that,” Rudd said.

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Rudd said Lake County State’s Attorney Mike Nerheim has a moral and ethical responsibility to reopen the case. Nerheim has said he sees no reason to do that.

Calusinski is serving a 31-year prison sentence for Kingan’s murder. She was caring for him at a Lincolnshire daycare center, when he became unresponsive in January 2009, and died.

Though Calusinski gave videotaped statements admitting she slammed Benjamin to the ground, her defense team argued that confession was coerced, and given only after police deprived her of sleep.

In addition to the doubts raised by Rudd, police video raises questions about Calusinski’s interrogation in 2009. Video of her police interview shows Calusinski being grilled by Lake County detectives.

Seventy-nine times, over the course of several hours, Calusinski denied any involvement in the death of the toddler.

Finally, after some nine hours, Melissa changed her story.

Defense attorney Kathleen Zellner said that confession is not valid.

“I know her confession doesn’t match the medical evidence,” Zellner said. “I know this needs to be completely reviewed.”

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In February 2014, a panel of the Illinois Appellate Court upheld Calusinski’s conviction, but Zellner has said they will file a new appeal, citing new medical evidence of the earlier head injury.