Cahill is accused of airing taxpayer-funded ads for the state lottery as a means of promoting his 2010 independent campaign for governor.
As treasurer, Cahill oversaw the state lottery. He is charged with violating state ethics laws and procurement fraud.
Cahill has said he did nothing wrong and that the ads were designed to promote the lottery, not his unsuccessful gubernatorial campaign.
Opening statements are scheduled Monday in Suffolk Superior Court.
Cahill’s former campaign manager, Scott Campbell, faces similar charges.