CHICAGO (CBS) — A Lake County judge has denied Melissa Calusinski’s bid for a new trial in the 2011 death of a toddler at a daycare center.

Lake County Judge Daniel Shanes, who sentenced Calusinski to 31 years in prison in 2011, said there was not enough new evidence to overturn her conviction for the death of 16-month-old Benjamin Kingan.

Prosecutors have said Benjamin died of a skull fracture caused by Calusinski, but defense attorneys have pointed to X-ray evidence showing he had a previous head injury missed by the initial autopsy.

Defense attorney Kathleen Zellner said the original X-ray files Calusinski’s attorneys received before trial were compressed to the point they were not legible, and newly discovered X-ray images showed Benjamin did not have a skull fracture when he died, but instead had a pre-existing head injury.

Last July, Lake County Coroner Thomas Rudd changed the official cause of Benjamin’s death from “homicide” to “undetermined,” citing the new X-rays. He said a previous injury caused the boy’s skull to enlarge at an alarming rate. In September 2008, his head size was in the 50th percentile, then the 75th percentile in December 2008 and the day after he died, January 15, 2009, the 95th percentile.

Dr. Eupil Choi, a pathologist who testified at Calusinski’s trial, has admitted he made a mistake, and that he missed a previous head injury during his autopsy on Benjamin.

However, Choi has said he wouldn’t change his mind that Kingan died from a severe head injury caused on the day he died. And prosecutors argued the X-rays cited by Zellner were not new evidence, but images the defense could have enhanced before trial.

Shanes agreed with prosecutors that the X-rays did not amount to new evidence, and rejected Calusinski’s request for a new trial, upholding her conviction.

Calusinski’s attorneys said they plan to appeal the judge’s ruling. After the hearing, Zellner said she was not surprised at Shanes’ ruling, and is grateful he made so many mistakes, saying he “totally missed the point” the defense was making.

The most damning evidence against Calusinski at her trial was her confession, given after six hours of interrogation and nearly 80 denials. Calusinski, who has a low verbal IQ, said detectives broke her down and she only told them what they wanted.

Calusinski has called her interrogation “a nightmare,” and said she only told detectives what they wanted to hear. She insists she never did anything violent and never struck Kingan.

Watch & Listen LIVE