Heavy Mechanics Pty Ltd, which had serviced the truck and trailer, is standing trial in the Wodonga County Court.

Jurors were on Thursday played evidence given by Leading Senior Constable Guy Tinsley, who spoke to truck driver Patrick Daley about what occurred.

"I just asked him if he was the driver of the vehicle and he said yes, he was," the officer said.

"He said he didn't know what happened, he just saw it come off and travel down the road towards the cars."

The driver's logbook was correct and he tested negative for drugs and alcohol.

Multiple police gave evidence in the trial on Thursday.

Detective Sergeant Darryl Out arrived at the Wodonga-Yackandandah Road site several hours after the crash on August 7, 2014.

Three people died in the collision.

The detective examined a nut from the towing components, which was found on the side of the road.

"There was areas on the thread that looked flattened and there were shards of steel," he said.

"The thread looked, in my opinion, the thread looked worn and stripped.

"It looked damaged."

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Detective Sergeant Out spoke of other wear and damage to components.

Leading Senior Constable Ian Ellis also attended.

A tow truck driver tested the Kenworth vehicle and the officer said "everything checked out fine".

Detective Acting Sergeant Philip Frith said he couldn't find any reference in service logs to the tow eye being replaced between June 17, 2011, until the final service six days before the crash.

The trailer travelled about 356,000 kilometres in that time, he said.

Defence lawyer Daniel Gurvich QC said the case centred what it was "reasonably practicable" for Heavy Mechanics to have done, and whether the prosecution would prove the steps taken by the company failed to reduce the risk.

"You've heard the expression 20-20 hindsight, and we've all got it," he said.

"And that's something to be cautious about as you hear evidence in this case, not to use hindsight."

Mr Gurvich said it was undoubtedly a tragic accident, but said everyone was entitled to the presumption of innocence, with jurors urged to keep an open mind.

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