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.

With four weeks in the rearview mirror, Brennan has yet to call several key witnesses from Read’s first trial, most notably: Michael Proctor, the lead investigator, Brian Albert

There was only a half day of testimony on Friday, with court wrapping up at 12:30 p.m. Medical examiner Dr. Irini Scordi-Bello finished testifying Thursday after several hours on the stand, during which graphic photos from John O'Keefe's autopsy were shown to the jury.