Heavy Mechanics Pty Ltd is on trial in the Wodonga County Court.

The company pleaded not guilty to a charge of failing to ensure people were not exposed to risk to their health or safety.

Defence barrister Daniel Gurvich said the trial was not about the collision, which occurred on August 7, 2014, but the risk involved.

He told jurors they should be satisfied the company had taken the measures they were required to.

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"In this case there has clearly been a tragic event, an unspeakable tragedy," he said.

"But it does not help to cast blame where it does not belong."

The court heard the case was about what was "reasonably practicable" for the company to do.

Mr Gurvich argued the business had done what was reasonably practicable.

He said the company had complied with a service sheet provided by BP.

"That's what happened," he said.

"That's what they did.

"They complied with their undertaking."

Mr Gurvich said the company was not undertaking the work of a scientist, metallurgist or engineer.

"You wouldn't hold Heavy Mechanics to a higher standard than any other mechanic in the community," he said.

"You wouldn't do it."

Mr Gurvich said "sometimes accidents happen and no-one is to blame", and said just because an accident happened didn't mean it was due to a failure by an employer.

"There may well have been pre-existing damage before it got to Heavy Mechanics," he said of one of the trailer components.

The court heard the company had no prior convictions, charges or adverse contact with WorkSafe.

Mr Gurvich said mechanic Richard Trethowan said he regarded the company "very highly", as did Arnold's Fruit Market managing director Roger Arnold.

Truck driver Patrick Daley considered Heavy Mechanics to be "very thorough" with safety "paramount", Mr Gurvich said.

Judge Christopher Ryan addressed jurors.

He said the circumstances of the case would draw on anyone's heart strings, but said they must assess the evidence dispassionately and with an open mind.