(CBS) — An Illinois Appellate Court panel has upheld the murder conviction of a Carpentersville woman accused of killing a 16-month-old boy at a Deerfield daycare center five years ago, but the woman’s father said it’s only a minor setback.

Melissa Calusinski, 27, is serving 31 years in prison following her 2011 conviction for first-degree murder in the death of Benjamin Kingan. Prosecutors had accused her of throwing Benjamin onto a tile floor on Jan. 14, 2009, at the Minee Subee daycare center.

On Wednesday, a panel of the Second District Illinois Appellate Court affirmed Calusinski’s conviction, rejecting arguments of ineffective counsel, abuse of the trial court’s discretion, and improper denial of Calusinski’s motion to suppress her statements to police.

It’s the third post-conviction ruling against Calusinski, but her father, Paul Calusinski, said “this is just a little bit of a setback.”

“Trust me when I tell you this, that we will go to a higher level. This is far from over,” he said. “We are going to continue our fight.”

Paul Calusinski said the ruling was not unexpected, because the appeal was filed before new information came to light, in the form of a sworn affidavit from a forensic pathologist – backed by two others in the coroner’s office – that Benjamin suffered brain injuries before Melissa allegedly killed him.

“We kind of, in a way, that this possibility was out there – that it would go 50-50 – because they didn’t have this information,” Paul said.

That pathologist, Dr. Eupil Choi, has admitted his trial testimony was mistaken, and that he missed a previous head injury during his autopsy on Benjamin.

“They did not have the information about Dr. Choi’s affidavit,” Paul said.

Ever optimistic, he said he believes his daughter ultimately will be found not guilty.

Though Melissa 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.