A crash reconstructionist is slated to return to the stand today in the Karen Read retrial for what promises to be a detailed cross examination when court opens for a 22nd day at 10 a.m. Watch proceedings in the player below.

Read, 45, of Mansfield, faces charges of second-degree murder, manslaughter while operating a motor vehicle under the influence, and leaving the scene of a collision causing death.

Judson Welcher, a PhD biomechanical engineer and accident reconstructionist with a company called Aperture, testified to the prosecution’s allegation that Read backed her car into John O’Keefe, causing his death.

After hours of testimony regarding his methods of analysis, prosecutor Hank Brennan asked him for his conclusion: Did Read’s Lexus LX570 strike O’Keefe at around 12:32 a.m. on Jan. 29, 2022, outside 34 Fairview Road in Canton?

“Yes, based on the totality of the evidence, DNA, everything I’ve talked about, that is consistent with that happening and within a reasonable degree of scientific certainty that is what happened,” Welcher said.

The line drew an immediate objection from the defense. Judge Beverly J. Cannone said she would release her ruling on its admissibility before court begins at 10 this monring.

This is a developing story.

Karen Read retrial Day 21: Expert testifies to John O’Keefe vehicle strike