During Karen Read’s retrial for the murder of Boston officer John O’Keefe, the presiding judge halted the defense’s last witness on Wednesday. The interruption happened after the witness, Dr. Andrew John Rentschler, made personal remarks about his children and wished his 10-year-old a happy birthday.

Dr. Rentschler, who is a biomechanical engineer and accident reconstruction expert with the firm ARCCA, began his testimony by sharing, “I have three children, including a 9-year-old who is turning 10 today – happy birthday Kai – along with two older ones.”

The testimony was quickly interrupted by Judge Beverly Cannone following an objection from special prosecutor Hank Brennan, as she instructed, “All right, we’re going to stop this – [let’s use] a different example instead.”

Brennan has repeatedly tried to have Rentschler’s testimony blocked or limited. The ARCCA scientists dispute the state’s version of events – and have also been accused of destroying text messages with the defense they were ordered to give to prosecutors as well as slow-walking discovery disclosures.

Dr. Judson Welcher, an accident reconstruction expert, testifies during the murder retrial of Karen Read in Norfolk Superior Court, Thursday, May 29, 2025, in Dedham, Mass. (Mark Stockwell/AP Photo, Pool)

Based on his testing, he said that he ruled out an impact with Read’s 2021 Lexus LX 570 SUV and O’Keefe’s arm as the cause of those injuries.

“They’re inconsistent with striking the taillight or being produced as a result of contact with the taillight,” he testified.

The prosecution claims that these minor injuries came from an impact with Read’s broken taillight after she allegedly drove into O’Keefe on Jan. 29, 2022 and left him to die on the ground in the snow.

The defense denies a collision and has claimed the injuries came from dog teeth and claws.

Aperture’s Dr. Judson Welcher testified earlier, based on digital forensics of phone and vehicle data, that Read’s SUV reversed at 75% throttle right before O’Keefe’s last conscious interaction with his cellphone.