Janice Bufton appeared before Justice Andrew Tinney at the Supreme Court in Horsham on Wednesday.

She will answer allegations she hit and killed her partner Colin Snooks, 70, in her driveway, with his own vehicle on October 31, 2017. She is pleading not guilty.

A witness to the incident, Benjamin Weston, has since died.

The court heard Mr Snooks had arrived at the property with Mr Weston about 12.30pm to collect his caravan, which was parked in Ms Bufton's driveway.

The court heard the pair allegedly quarreled and Ms Bufton got into Mr Snooks' vehicle and drove it to the back of her house.

Mr Snooks began to walk up the driveway with Mr Weston. He instructed Mr Weston to call Triple Zero, and then took the phone and told the emergency responder there was a domestic dispute.

At that point, Ms Bufton is alleged to have driven the vehicle back around the house and towards the pair until she hit Mr Snooks, who allegedly had moved off the driveway onto an adjacent grassy verge in an effort to avoid the oncoming vehicle. He died at the scene.

Mr Weston was not harmed.

Ms Bufton, 66 at the time of the incident, was in a de facto relationship with Mr Snooks. They lived together on-and-off from January 2016.

Both the prosecution and the defence told the court that the pair had an "on-again, off-again" relationship which came to a head on October 31.

Prosecutor Kevin Armstrong told the court that he would argue Ms Bufton intended to strike Mr Snooks in order to cause serious harm or kill him.

Mr Armstrong said several witnesses would demonstrate the abuse Ms Bufton allegedly dealt Mr Snooks - both physical and verbal.

Mr Armstrong also alleged that Ms Bufton believed Mr Snooks was cheating on her with his ex-wife.

"It was sometimes a volatile relationship," Mr Armstrong said.

Mr Armstrong told the court that a witness would describe a visit from Mr Snooks two days before the incident, in which Mr Snooks allegedly told the witness things were bad at home.

Mr Armstrong told the court that the Major Collision Investigation Unit determined the vehicle had been travelling at "at least 45 kilometres" when it struck Mr Snooks, and no faults were found with the vehicle that could have contributed to the incident.

He said that officers found three distinct changes of direction could be traced on the driveway to the point where the vehicle struck Mr Snooks.

Defence lawyer Tom Danos said the defence did not contest the volatile nature of the relationship, but contested the notion that Ms Bufton was abusive.

Mr Danos alleged that Mr Snooks was not a victim of abuse; rather a man able to stand up for himself.

"That she was so angry with his behaviour that she was out wreaking revenge - that is very much in issue," he told the court.

Mr Danos also described various medical issues Mr Snooks had faced which caused him to be unsteady on his feet.

Mr Danos argued this was an unfortunate and unintentional incident, whereby Ms Bufton was in fact trying to avoid Mr Snooks but was ultimately unable to.

"It's unfortunate that his evasive action was in the wrong direction," he told the court.

"In fact, that's why she was driving down the grass verge - to avoid him."

Another key element of the case will be the validity of Mr Weston's statement, given via video.

He had visited the site the next day with police and walked them through what he believed had happened. This was recorded and played for the court on Wednesday.

However, Mr Weston has since died in unrelated circumstances. Justice Tinney said because Mr Weston had died before he could be cross-examined, the defence was expected to "take strong issue with that evidence".

The trial is expected to take several days.

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