A forensic scientist returned to the witness stand for cross-examination in Karen Read's second murder trial, as Read's defense team seeks to cast doubt on the reliability of key pieces of evidence. Read, 45, is accused of hitting her boyfriend, Boston Police Officer John O'Keefe with her Lexus SUV and leaving him to die in the snow outside the home of a fellow cop in January 2022. Prosecutors say Read deliberately hit O'Keefe, 46, in a drunken rage. Her lawyers say she was framed for O'Keefe's death in an elaborate conspiracy devised by Massachusetts police officers. Maureen Hartnett, a forensic scientist with the Massachusetts State Police Crime Laboratory previously testified about her examination of Read's vehicle just days after O'Keefe's death on Jan. 29. Photos from her inspection of the vehicle showed a smashed taillight, with chipped paint, scratches and dents covering the back of the vehicle where prosecutors say Read struck O'Keefe. Read's defense probed Hartnett about how small pieces of the taillight remained in place for several days during a snowstorm after Read's car was seized by police. They questioned her about whether she found blood or biological material under the SUV -- she did not. The testimony comes weeks into the trial in which prosecutors have sought to showRead's heavy drinkingthe night before O'Keefe died, her frantic behavior the day his body was found andprofanity-laden voicemailsshe left for the Boston police officer. Here's the latest from Day 16: CourtTV has been covering the case against Read and the criminal investigation since early 2022, when O'Keefe's body was found outside a Canton, Massachusetts home. You can watchCourtTV's live feed of the Read trialproceedings from Norfolk Superior Court in Dedham, Massachusetts. Proceedings begin at 9 a.m. ET. This article originally appeared on USA TODAY:Karen Read trial live: Defense probes forensic scientist on evidence