The sister of a 20-year-old who caused a triple fatal crash in Coromandel has taken matters to the High Court to prevent her estranged mother from cremating her brother's body.

Haydn Clark's father, James Clark, remains in Auckland's Middlemore Hospital following the crash on April 19, which killed his son as well as two Thames locals.

Clark, from Drury, was driving the ute that police say crossed the centre line and collided with a car in which Jocelyn (Anne) Fielder, 64, and her husband Ian, 66, were travelling.

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All three were killed in the crash near the Kopu Bridge on State Highway 25.

Clark was facing methamphetamine charges and was on bail, including a 24-hour curfew order.

According to court documents from a hearing last Tuesday, Clark's sister Jessica Clark made a application on behalf of her father, who remains in care in Auckland's Middlemore Hospital.

He had been recovering from critical injuries suffered in the crash, and had not yet had the chance to see his son's body.

Clark's mother, Brenda Cottingham, had given an undertaker in Waihi full authority to cremate her son's body - following a funeral she had organised for last Tuesday.

Jessica Clark's evidence, given around midday Tuesday in court, was that neither she, nor her father, had been consulted.

The judge also notes Haydn Clark's partner of three years, Gabrielle, had not been consulted either.

"I understood from the advice I received that James Clark and Brenda Cottingham separated when Haydn was under the age of 4. When Haydn was aged 4 he was placed in the care of a family friend where Haydn remained for approximately four to five years," Judge Woodhouse noted.

"I was told that the understanding of those in Court, including Jessica Clark, was that Haydn had seen very little of his mother over the last three years or so."

The application to halt the cremation of the 20-year-old's body was heard under "real urgency", the documents note, as the judge heard it just hours before the cremation was scheduled.

Along with this, plans to hold a funeral service in Waihi last Tuesday afternoon were also brought to a halt.

"Jessica Clark stated that her father did not want the cremation to proceed at this time," Judge Woodhouse said.

"Apart from anything else, he has had no opportunity to see his son's body."

"He has apparently told his daughter that what he wants, once he has seen his son's body, is for a service to be held in the chapel at Middlemore Hospital, with appropriate arrangements for disposal of Haydn's body to follow."

Judge Woodhouse said James and Jessica Clark could apply for further orders in respect to the disposal of Haydn's body - which would be taken to Middlemore Hospital.

"I was satisfied that this is a case justifying an application without notice and then justifying the making of the orders," he said.

Cottingham had the opportunity to make an application of her own, by the end of last week.

A post on Haydn Clark's Facebook page shows he crashed a car in 2014 and suffered a broken neck, which required a hospital stay and him to wear a "halo" head brace.

One post refers to him losing his driver's licence, having a vehicle green stickered for not complying with road rules and stating that he owed more than $1000 in fines.

In August 2015 he posted a picture of a mangled car with the caption saying it was about a year since he wrote it off.

Friends jokingly commented he "still hadn't learned", with another saying he was lucky to be alive.

Clark commented saying he had learned his lesson since the 2015 accident, adding he had "munted that car".

Clark had posted several videos of car-related stunts, including one in April 2016 where a car was shown speeding down a road, spinning out and leaving plumes of smoke in its wake.

The month before he had posted a video with a car he said was at his house pulling a similar stunt.

"Lazy drivway skid at mine [sic]," he said.

Another post asked whether anyone "got any vids of me doing skids in the corvette can u post them? [sic]"

Several posts referred to incidents where Clark had appeared in court or had altercations with police.