The Crown prosecutor in the trial of Christy Natsis, a Pembroke dentist charged with impaired driving causing death, is hoping a judge will rule an OPP constable's testimony as expert testimony.

The Crown called on Const. Jeff Hewitt Wednesday after two days of testimony from Ford automotive engineer Jim Engle.

Natsis has pleaded not guilty to charges of impaired driving and dangerous driving causing death after her SUV struck another vehicle in 2011, killing the driver, Bryan Casey.

Crown prosecutor John Ramsey took two hours to go over — in exacting detail — Hewitt's resumé and training.

OPP Const. Jeff Hewitt

OPP Const. Jeff Hewitt is the crash reconstructionist who looked at the 2011 fatal collision that killed Bryan Casey. (CBC)

Hewitt is a crash reconstructionist who produced a report on the fatal crash involving Natsis's vehicle.

The Crown wants to ensure Hewitt's credibility remains intact.

Earlier in the trial, defence lawyer Michael Edelson attacked the testimony of Const. Shawn Kelly, the OPP's lead traffic investigator.

Edelson presented emails that he said show the officer blurred the lines between an investigator seeking a conviction and an impartial expert. He argued that Kelly's testimony should not be admitted.

Kelly had testified the crash occurred in the lane of the driver but also admitted he'd made mistakes in his report.

With that setback to their case, Crown prosecutors hope the testimony from their latest witness will help convict Natsis.

Justice Neil Kozloff said he will rule at a later date if the OPP constable's testimony can be accepted as expert testimony.

The Crown said they have four more witnesses to call after Hewitt, each of them from the OPP.