A special crimes unit investigator for the Quebec provincial police told a jury at the Sherbrooke courthouse Tuesday he was the first uniformed officer to arrive at the scene of the devastating train wreck in Lac-Mégantic on July 6, 2013 — almost eight hours after the derailment and explosions.

Pierre Fortier is the third Crown witness called to testify at the trial of former train engineer Thomas Harding, 56, controller Richard Labrie 59, and operations manager Jean Demaître, 53.

The three former employees of Montreal, Maine and Atlantic Railway (MMA) are charged with 47 counts of criminal negligence causing death in connection with the disaster.

Dressed in a tailored grey suit, the Sûreté du Québec investigator described how he got a call from his supervisor just after 5 a.m. on July 6 at his home in Trois-Rivières, with orders to pack a bag and head to Lac-Mégantic.

He said his task was to find and seize the missing locomotives, which had become detached from the tanker train that had barrelled into the centre of town and derailed just before 1 a.m., causing a series of explosions.

Fortier told the court when he found the locomotives and a caboose, he immediately treated the area as a crime scene. 

"I could smell an odour of burnt metal," he said. "There was oil spraying out of one of the locomotives. It completely ruined the clothes I was wearing."

Defence loses patience with witness

Under cross-examination, Fortier was asked by Gaétan Bourassa, the defence lawyer for Demaître, if he'd taken notes on the number of police officers present that morning.

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Smoke rises from railway cars that were carrying crude oil after derailing in downtown Lac-Megantic, on July 6, 2013. (Paul Chiasson/Canadian Press)

Fortier said he hadn't, explaining that as the first uniformed officer on the scene, he'd been thronged by more than 30 people he said were in ''crisis.''  

''I was moved," he said. "I met a girl who was sure she had lost her boyfriend, she said her boyfriend had gone to a ciné-café the night before."

Bourassa became visibly upset with Fortier's response, telling him that his explanation wasn't an answer to his question.

He posed several more questions, asking Fortier each time, "Do you understand the question?"

Fortier was also questioned by one of Harding's lawyers, Charles Shearson, about earlier testimony, in which the SQ investigator recounted allowing MMA employees to enter the locomotive to take photographs of what had occurred.

Fortier had said that he'd seen those employees going through a bag of documents and had ordered them not to touch them.

Shearson demanded to know how Fortier was certain that no documents had been taken.

Fortier said he hadn't seen them take any.

Earlier Tuesday, defence lawyers cross-examined Jacques LaFrance, an SQ crime scene technician dispatched to Lac-Mégantic on the day of the disaster.

Guy Poupart, Labrie's lawyer, fired a barrage of questions about the dozens of photos of the wreckage LaFrance took in Nantes, the village 13 kilometres from Lac-Mégantic where the train had been parked on a siding overnight, and at the site of the derailment.

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The centre of Lac-Mégantic was destroyed and 47 people died after a runaway train carrying crude oil derailed, causing a series of explosions, on July 6, 2013. (Reuters)

Poupart focused on the fact that SQ investigators were working closely with inspectors from Transport Canada — including Alain Richer, who Poupart said had inspected the ill-fated train the day before the derailment.

Poupart wanted to know if Lafrance was aware of that.

Lafrance said he was.

Thomas Walsh, another of Harding's lawyers, picked up the same line of questioning.

He asked if there had been discussions with the Transport Canada employees ''about the possibility that there was a level of fault in this event, for example, by not monitoring MMA properly?''  

Lafrance said that wasn't a subject they were permitted to discuss.

A fourth Crown witness, an MMA communications technician, has now begun his testimony.

The trial before Superior Court Justice Gaétan Dumas resumes in Sherbrooke on Wednesday.