A Pembroke woman on trial for impaired driving causing death did not hit the brakes in the moments before a fatal head-on crash on Highway 17 two years ago, an automotive engineer testified Wednesday.

Dr. Christy Natsis is charged with impaired driving causing death, dangerous driving causing death and exceeding the legal blood-alcohol limit in the March 2011 crash on Highway 17 that killed 50-year-old Bryan Casey of Ottawa. Natsis has pleaded not guilty to the charges.

The crash on Highway 17 between two SUVs left one man dead. (Supplied photo)

Her trial on Wednesday turned to the testimony of Jim Engle, an automotive engineer with the Ford Motor Company and an expert witness in more than 20 trials.

Prosecutors brought in Engle to analyze the data from the power control module of Dr. Christy Natsis's Ford Expedition, which acts as a type of black box for the vehicle.

The recorder did not show any indication she touched her brake in the seconds leading up to the collision, said Engle. It also showed Natsis was travelling at about 88 km/h at the moment of impact, he said.

Some data lost, engineer says

The power train control module typically records about 95 seconds before a crash and about five seconds afterwards. But in this case, there were two failures. The machine failed to flag the moment her vehicle's airbags deployed and about 30 seconds of data was later overwritten by error.

But the errors did not compromise the information during the crucial period before the impact, said Engle.

Engle's testimony had to wait until he could be sworn in as an expert witness.

On Tuesday, defence lawyers questioned why he had not been introduced as an expert and when he was, they questioned his credentials. But the judge did decide the engineer needed to be heard and he was qualified to interpret and analyze the data on the device.