An Ontario Provincial Police crash investigator has denied his findings about a fatal impaired driving case were based on colleagues' opinions.

OPP Const. Jeff Hewitt has been testifying for a day and half at the trial of Dr. Christy Natsis of Pembroke.

Natsis is facing charges of impaired driving causing death, dangerous driving causing death and exceeding the legal blood-alcohol limit in the 2011 fatal collision that killed Ottawa man Bryan Casey.

But Hewitt has yet to present his findings, as defence counsel have challenged whether he should be considered an "impartial" expert witness.

Defence lawyer Michael Edelson asked Hewitt to comment on email comments made by the lead crash investigator who testified in March.

Officer asked about 'vested' interest email

In it Const. Shawn Kelly called for a meeting of colleagues about a "high profile case" of which they all had a "vested" interest in.

Edelson asked Hewitt if he was surprised by Kelly referring to his OPP colleagues having a "vested" interest.

OPP Const. Jeff Hewitt

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

"The way you have describe it — yes," said Hewitt.

But he denied he incorporated the opinions from fellow crash investigators into his report.

"I write my reports based on my training not someone else's opinion," testified Hewitt.

Edelson also asked Hewitt if he's bound by ethical guidelines in writing his report.

He answered: "I present physical evidence, not to put a lean on it one way or the other."

Edelson said because Hewitt's original draft report was destroyed or deleted the court won't know for sure.

Hewitt responded it is OPP policy not to save original drafts.

Crown attempting to qualify Hewitt as expert witness

The Crown is attempting to qualify Hewitt as an expert witness, while the defence continues to challenge that designation with Justice Neil Kozloff.

Last week, defence lawyer Michael Edelson and his team were given until Tuesday to review notes by an OPP crash investigator that hadn’t been disclosed to them.

The trial reaches the one-year mark this week, although less than one fifth of that time has actually been spent in the courtroom.

One of the reasons the case has taken so long is the trial has called for multiple breaks, including a scheduling-related stoppage of over five months which only recently ended.