A trailer containing Tim Bosma's truck, key evidence in the murder trial of the two men accused of killing him, was left unsecured during transport to an Ontario Provincial Police facility, court heard Wednesday — allowing a box to fly out the rear doors onto the highway, where it was run over by an unmarked police car.

The trailer with the Ancaster, Ont., man's truck inside was being transported from a secure facility in Hamilton to an OPP forensics facility in Tillsonburg, Ont., for examination on May 14, 2013.

Det. Const. Lauren Troubridge was tasked with following the trailer as it was towed. On Highway 403, at the Golf Links Road overpass, the rear doors of the trailer flew open while travelling around 110 km/h, Troubridge testified in court Wednesday.

This was around 6:30 p.m.

"It was very heavy traffic at that time," she said, adding that a cardboard box fell out of the trailer and she ran over it with her car.

"The lock wasn't actually securing the doors closed," she said, elaborating that the bar across the back of the trailer didn't secure the doors properly.

Const. Brent Gibson testified that on May 12, 2013, he locked the trailer with his own lock. During cross-examination, Troubridge agreed that the doors "apparently" weren't secured as they should have been.

Bosma family

Sharlene Bosma (centre) enters the courthouse flanked by friends and family on Wednesday. (Rob Krbavac/CBC)

Troubridge said that once she saw the doors fly open, she honked her horn — but the tow truck driver didn't notice. She changed lanes, sped up next to the driver and got his attention to pull over.

Dellen Millard, 30, of Toronto, and Mark Smich, 28, of Oakville, Ont., have pleaded not guilty to first-degree murder in the death of the 32-year-old father from Ancaster, Ont., whose body was found burned beyond recognition.

Millard's lawyer, Ravin Pillay, seized the opportunity in court Wednesday to point out that Troubridge couldn't say if anything else had fallen out of the trailer or been disturbed once she wasn't travelling behind it.

"You don't know if anything else came out, because you weren't watching it, correct?" he asked.

Troubridge said she believed the box was the only thing that fell out.

Doors secured with wire, not another lock

She went back to the same area of the highway that night to look for the box and believes that she found it.

"You don't know if it's the same box," Pillay said during cross-examination.

"I know it's the same box, I saw it come out of the trailer," she said. But it had also been driven over by several cars, she said.

A second box was also recovered by police, but Troubridge said it didn't come from the truck. 

Bosma truck Millard trailer

Bosma's truck was found inside a trailer at the home of Dellen Millard's mother, police officers testified. (Halton police/Court exhibit)

After the tow truck driver pulled over, he secured the trailer doors with a piece of wire he had in his truck, Troubridge testified.

Pillay also questioned that decision in cross-examination.

"You didn't secure the trailer at that moment with another lock?" Pillay asked.

"I didn't have one," she answered.

Pillay also asked if she could have called for backup from the side of the road and used another lock.

"I guess I could have done a few things, but I secured it with a wire. That's all we had," she said.

Millard's fingerprint found on truck

Court also heard Wednesday from a second fingerprint expert, who testified that Millard's fingerprint was found on the driver's side door of Bosma's truck.

"It is my opinion that the unknown impression on Tim Bosma's truck was authored by the left ring finger of Dellen Millard," said Det. Const. Colleen O'Rourke from Halton Regional Police.

Another fingerprinting expert previously testified that Millard's thumbprint was also found on the truck's rear-view mirror.

The court's afternoon session centred on a presentation from Phillip Wilkinson, who works with the OPP's analytical support team as an intelligence analyst.

Tim Bosma

Bosma vanished while trying to sell his truck online in May 2013. (Facebook)

Wilkinson created an extensive presentation that maps the cellphones registered to Millard, Smich, Lucas Bate (whom police have never found), Smich's girlfriend Marlena Meneses, Millard's girlfriend Christina Noudga, and Tim Bosma.

The entire presentation wasn't finished before court adjourned on Wednesday (which means it wasn't released in its entirety for the public to see), but the jury did hear evidence about the locations of those phones and how they moved in tandem up to and including the night that Bosma vanished.

According to the presentation, Millard's phone and Bate's phone were pinging off cell towers close to each other at similar times on May 6, 2013. 

At 9:02 p.m. that night, Millard's phone pinged off a Rogers tower in the area of the Bosma home in Ancaster. Then at 9:05 p.m., Bate's phone called Bosma, and pinged off a cell tower about two kilometres away.

That call to Bosma was the last recorded call the phone registered to Bate ever made.

Around 9:20 p.m., the Smich phone was also pinging off a Rogers tower in the area of the Bosma home, court heard.

The trial continues Thursday morning.

CBC reporter Adam Carter is in the courtroom each day reporting live on the trial. You can view a recap of his live blog here:

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