A Superior Court judge will deliver a ruling on whether McCallion broke the conflict guidelines when she voted on matters that could've helped her son's business.
It could result in the 92-year-old mayor being turfed from office.
It's expected Justice John Sproat will release his much anticipated decision at 10 a.m.
Since mid-April, Sproat has been reviewing evidence on whether McCallion breached the Municipal Conflict of Interest Act.
McCallion is facing allegations she voted at Peel Regional Council to help her son's company avoid paying higher development fees.
Peter McCallion's company World Class Developments proposed building a hotel and convention centre in downtown Mississauga.
The mayor testified she didn't know her 2007 vote would help his company.
Municipal legal expert John Mascarin says he believes McCallion will survive.
"The evidence is just that she just did not know that her son was sufficient to trigger the deemed interest provisions under the Act," he said.
Mascarin says the fact that McCallion has served her community for more than three decades will likely play into the judge's decision.
McCallion wasn't available for comment. She was returning from a South American trade mission in Brazil, but her lawyers say she will hold a news conference at 11:30 a.m. to respond to the report.
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