The first witness called by Karen Read's defense explained that there were few scenarios where John O'Keefe's phone locked before Read's car accelerated in reverse.

In the trial of Karen Read, accused of killing John O’Keefe, defense scrutinizes crash expert's costly experiments and presentation modifications for inconsistencies.

The Karen Read trial is now in the hands of the defense, which called its first witness Friday. The prosecution rested its case in the high-profile Massachusetts murder trial on Thursday after weeks of testimony from 38 witnesses.

Prosecutors rested their case after calling a witness responsible for explaining exactly how the supposed collision between Karen Read's SUV and John O'Keefe took place.

Prosecutors rested their case after Dr. Judson Welcher, a crash reconstructionist expert with Aperture LLC, was dismissed from the stand after three days. He most notably testified to the prosecution that damage to Read’s SUV was “consistent with a collision” involving O’Keefe if the vehicle was moving faster than 8 mph.

Karen Read’s defense team will begin callings its own witnesses after the prosecution rested its case Thursday. Follow the proceedings in the live video here.

Aperture, the company Welcher works for, created digital images of O’Keefe’s driveway as part of their analysis of whether Read’s SUV could’ve been cracked when it backed up into O’Keefes Chevrolet the morning he died.

The prosecution in Karen Read’s murder retrial filed a motion on Wednesday asking Judge Beverly Cannone to remove a key piece of evidence from the court record.