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.

Read is accused of backing her SUV into her Boston police officer boyfriend, John O’Keefe, and leaving him for dead.

Massachusetts State Police forensic scientist Maureen Hartnett is back for additional testimony in Karen Read's murder retrial.

Read is accused of backing her SUV into her Boston police officer boyfriend, John O’Keefe, and leaving him for dead.

The high-profile Karen Read trial is back inside a Dedham, Massachusetts courtroom with more witness testimony.