David Noel Roigard is sentenced at New Plymouth High Court on Monday, February 15 for killing his son, Aaron Roigard in 2014.

A coastal Taranaki farmer has been sentenced to life in prison in the High Court at New Plymouth for the evil act of killing his son to cover up the theft of tens of thousands of dollars.

David Roigard, 51, will serve a minimum non-parole period of 19 years.

Roigard appeared before Justice Paul Heath on Monday for sentencing on one charge of murder and eight of theft in a special relationship.

Dressed in a black t-shirt and grey tracksuit pants, Roigard showed no emotion and stood with his hands clasped in front of him.

READ MORE

* Murder victim's partner determined to keep his memory alive

* Roigard trial: Father found guilty of murdering son

* Roigard: Defence dismisses Crown's claim of murder plot

* Roigard Murder Trial: Crown say murder was a calculated cover up

* Roigard Murder Trial: Week Four

Heath said there were no mitigating factors.

"You do not accept responsibility for what you did, you show no remorse, you show no understanding of the enormity of your deceit and the evil act of killing your own son, you were not prepared to tell the police when they asked where the body could be found," he said.

A jury took about six hours to find Roigard guilty of killing his son Aaron Roigard in December following a trial that lasted more than four weeks.

Roigard murdered Aaron on June 2, 2014, after stealing more than $66,000 from the 27-year-oldover a number of years.

Aaron's body has never been found, but is believed to be buried somewhere in rural South Taranaki.

Crown prosecutor Cherie Clarke said the aggravating factors included the fact that the murder involved actual violence and the use of at least one weapon - a wood splitter.

She said Aaron was killed by David Roigard in an attempt to avoid detection and prosecution for the theft, which took place over a period of seven-and-a-half years.

"The crown submits that this was truly a cruel, depraved and callous murder.

"The offender told others that the deceased deserved everything he got and the deceased would never be found."

Clarke said Roigard had shown no empathy since committing the murder.

"This proves that the offender truly did act when murdering his son, to use your honour's own words that you have used in previous cases, that he did so with a numbness of the soul."

She said Roigard's refusal to disclose where Aaron's body was buried was a serious aggravating factor.

"It shows the degree of depravity, cruelty and callousness."

Clarke sought a non-parole period of between 20 and 22 years' imprisonment.

Defence lawyer Paul Keegan said Roigard's position had not changed since his trial.

"He denies the murder of his son," Keegan said.

Roigard accepted that he must be sentenced in accordance of the jury's verdict and a life sentence would be imposed, he said.

Keegan said a 17 year non-parole period was sufficient.

"To extend beyond that would be unwarranted in the circumstances in this case."

Heath said the only issue for his consideration was the length of time Roigard would have to serve before he could first apply for parole.

He said Aaron was a simple soul who was prepared to rely on his father to safeguard his interests by looking after his money and making sure he had sufficient to buy his own farm.

"Aaron trusted you. You betrayed that trust."

Heath said he was satisfied from the evidence given during the trial that there was no reasonable possibility Aaron is still alive.

"I am satisfied that his body would likely have been located had he committed suicide.

"Once the fact that Aaron was dead was established there was no other candidate as his killer."

Heath said a psychiatric report confirmed the view he formed about Roigard during the trial - that he suffered from anti-social and narcissistic personality disorders.

He said there were no mitigating factors.

"You do not accept responsibility for what you did, you show no remorse, you show no understanding of the enormity of your deceit and the evil act of killing your own son, you were not prepared to tell the police when they asked where the body could be found."

Heath sentenced Roigard to three years and six months on each of the theft charges, which are to be served concurrently.

The conviction is believed to be the first murder case to be prosecuted in Taranaki without a body.

*Verdict in full - click here