WAUKEGAN, Ill. (STMW) — Claiming a key prosecution witness lied about his credentials, Melissa Calusinski’s attorneys argued Thursday the former daycare worker convicted of murdering a toddler deserves a new trial.

A pathologist who examined 16-month-old Benjamin Kingan didn’t tell jurors hearing the trial that he had failed an exam to become board-certified, defense attorney Paul DeLuca said, arguing Calusinski’s rights were violated because that information could have affected the impact of his testimony.

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“He lied to the jury,” DeLuca said of Dr. Manny Montez, who graphically described for jurors the brain and skull injuries that caused the boy’s 2009 death. “Dr. Montez was a significant witness for the state.”

But Lake County Judge Daniel Shanes on Thursday rejected the request for a new trial, saying he didn’t believe the omission violated Calusinski’s rights to a fair trial, the Sun-Times is reporting.

“I just don’t see how the defendant was prejudiced,” Shanes said as he refused to overturn Calusinski’s November murder conviction.

And Shanes, who at one point dismissed the dispute as “much ado about nothing,” pointedly said he didn’t believe Montez misrepresented his medical background when questioned by defense attorneys during her trial.

“I do not find Dr. Montez lied. There is no perjured testimony in that regard,” Shanes said.

DeLuca and co-counsel Dan Cummings said they were “disappointed” by the ruling and expect to raise the issue when they appeal Calusinski’s murder conviction and 31-year prison sentence.

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Calusinski was convicted of killing Benjamin on Jan. 14, 2009 when she became frustrated and hurled him to the floor at the Minee Subee daycare center in Lincolnshire.

Montez and other doctors testified the 22-pound boy suffered fatal brain and skull injuries that appeared to have been inflicted when his head hit a tile floor.

When questioned by DeLuca during the trial, Montez testified he was not board-certified in pathology, saying he hadn’t taken the required exam.

Medical records subpoenaed after the trial indicate he failed a board exam in anatomic pathology in 2001 and hadn’t taken an exam for forensic pathology, defense attorneys said.

Jurors should have been told those details about Montez’s medical background to better understand his expertise, defense attorneys argued.

“Our client’s due process rights were violated by this witness lying,” said DeLuca, who argued during the trial that other medical evidence indicated the Deerfield boy could have suffered from prior, undiagnosed brain bleeding that contributed to his death.

Montez couldn’t immediately be reached for comment, but prosecutors contended he didn’t lie because he told jurors he was not board-certified. The details of that lack of certification wouldn’t have affected the jury verdict, prosecutors said.

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“It didn’t matter to the case,” Assistant State’s Attorney Christen Bishop said.