The judge overseeing Karen Read’s retrial on murder charges in the death of Boston cop John O’Keefe cut off the defense’s final witness Wednesday morning after he told jurors he had three children and wished his 10-year-old a happy birthday.

“So I was going to say I have three kids, a 9-year-old who’s actually turning 10 today – happy birthday Kai – and I have two older ones,” said Dr. Andrew John Rentschler, a biomechanical engineer and accident reconstructionist from a firm called ARCCA.

“All right, I’m going to, we’re going to stop this – [use] another example,” said Judge Beverly Cannone after an objection from special prosecutor Hank Brennan.

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.