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. The trial is entering its second week as the prosecution continues to call key witnesses.

Following testimony, Judge Beverly Cannone will hold a hearing on defense expert witnesses who found that John O’Keefe’s injuries weren’t consistent with being hit by a vehicle.

After opening arguments from Read’s defense attorney Alan Jackson and the Commonwealth’s special prosecutor Hank Brennan, a key witness was called to the stand.