Lindsay Clancy Judge Rejects Mistrial Bid in Murder Trial

Lindsay Clancy will not be getting a mistrial ... after the judge shot down her defense team's request Monday following controversial testimony about religion.

The drama unfolded during testimony from forensic psychologist Dr. Kirk Heilbrun, who brought up Clancy's belief that she and her children would be together in heaven ... and referenced Catholic teachings on suicide being a "mortal sin."

Clancy's attorney immediately objected and asked for a mistrial, calling the testimony "over the top ... talking about religion, talking about heaven, talking about killing people and the impact it would have on Lindsay as well as her children."

But Judge William Sullivan said no dice.

He denied the mistrial request ... though he did reprimand prosecutors and told jurors Heilbrun's comments were "immaterial, irrelevant and to be disregarded."

The jury was then sent home for the day.

Clancy has pleaded not guilty to first-degree murder in the deaths of her three children -- 5-year-old Cora, 3-year-old Dawson and 8-month-old Callan.

Prosecutors say Clancy planned the killings ... while her defense argues she was overmedicated and suffering from postpartum psychosis at the time.