Maureen Hartnett, a forensic scientist at the Massachusetts State Police crime lab, spent the most time on the witness stand Wednesday, the 15th day of trial. She said she was called to the Canton Police Department on Feb. 1, 2022, to examine the exterior of the alleged murder weapon: Read’s Lexus LX570 SUV.

The Karen Read murder trial is continuing a multiday look at forensic evidence with testimony from scientists that victim John O’Keefe contributed to DNA found on the Read’s SUV and