Karen Read's second trial started Tuesday with opening statements and witness testimony in the Massachusetts murder case.

Karen Read pleaded not guilty to murder charges in the death of Boston police officer John O’Keefe and is facing a retrial after a jury was unable to reach a verdict last year.

Karen Read’s second murder trial began Tuesday with a prosecutor saying the defendant’s own words will bolster evidence that she killed her police officer boyfriend three years ago and a defense attorney calling the case “the definition of reasonable doubt.