A former prison guard jailed for life for murdering his childhood friend will be treated just like any other prisoner, Corrections says, but can ask to be voluntarily segregated. 

David Charles Benbow was jailed for life with a minimum non-parole period of 17 years on Tuesday for murdering Michael McGrath in the Christchurch suburb of Halswell in May 2017. 

In October, after an earlier hung jury, Benbow was found guilty in the High Court at Christchurch. 

The Crown alleged Benbow murdered the 49-year-old after finding out he was in a relationship with his partner of 17 years, Joanna Green. 

McGrath was supposed to visit Benbow about 9am on May 22, 2017, to help him move some railway sleepers. Benbow said he never showed up, however, the Crown said the sleepers were a “ruse” and that once he arrived Benbow killed him with his .22 rifle and later disposed of his body. McGrath’s body and the firearm have never been found. 

Meanwhile, the defence said McGrath never showed up and that Benbow was in no better position than anyone to say what happened to him. 

At the time of McGrath’s murder, Benbow was a prison guard at Christchurch Men’s Prison. 

A Corrections spokesperson told the Herald following sentencing that when it came to prisoners safety was their “top priority”. 

“We have policies and operational procedures in place to support the safe, secure and humane management of all prisoners. 

“Former Corrections staff members who are sentenced to imprisonment are managed the same way as other prisoners. Like other prisoners, their specific circumstances and level of risk will determine where they are placed, and how they are managed.” 

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David Benbow was jailed for life in the High Court at Christchurch on Tuesday for murdering Michael McGrath. Photo / Alden Williams. 

In accordance with the Corrections Act, prisoners can be lawfully denied association with other prisoners if their behaviour presents a risk to the security of the prison, the safety of others, or if it is considered it is necessary to assess or ensure their mental or physical health. 

“Prisoners in New Zealand have the ability to request to be placed in voluntary segregation for the purpose of protective custody. This may be due to the prisoner fearing for their own safety or in order to be removed from gang members as they are trying to rehabilitate away from this lifestyle.” 

A prisoner can withdraw from voluntary segregation at any time. 

“A prison director can also direct the prisoner into voluntary protective segregation, without the prisoner requesting it, if they believe the safety of the prisoner has been put at risk by another person; and there is no reasonable way to ensure the safety of the prisoner otherwise than by giving that direction.” 

Segregated prisoners are provided with minimum entitlements set out in the Corrections Act. 

“They also have regular and ongoing contact with Corrections staff, including our health services staff and mental health professionals as required.” 

Christchurch builder Michael Craig McGrath, 49, was last seen at his home in Halswell, Christchurch, in May 2017. 

‘Calculated’ murder 

At sentencing, Crown prosecutor Barnaby Hawes said the victim impact statements showed the “devastating effects” of what happened. 

A key issue for sentencing was whether this case falls into category of murders especially bad that it required a minimum period of imprisonment of at least 17 years without parole. The Crown asked for a minimum period of 19 years in prison. 

“The murder of Mr McGrath involved calculated and lengthy planning in the way in which he was executed.” 

Crown said there was a significant aggravating factor that Benbow must know where McGrath is and what happened to him. 

“Mr Benbow could still say even now what occurred.” 

Benbow’s defence lawyer, Kirsten Gray, told the court it was acknowledged that McGrath was a “much-loved brother, son, and friend”. 

“But on Mr Benbow’s behalf, he appears before the court to be sentenced in accordance with the jury’s verdict. 

“He maintains he did not kill Mr McGrath. But in accordance with the jury’s verdict, he accepts he will be sentenced to life imprisonment.” 

The issue, Gray said, was that the minimum term of imprisonment should be. 

She said the court must consider Benbow’s personal circumstances. He is 55 years old, with no prior criminal convictions. 

“He was an engaged and loving father…” she said. 

Benbow was remanded in custody for more than two years, with considerable delay in trial from his arrest. None of those delays were his fault, she said. 

Gray said that the minimum term of imprisonment should be around 14 years, acknowledging an uplift due to the body not being located. 

Sam Sherwood is a Christchurch-based reporter who covers crime. He is a senior journalist who joined the Herald in 2022, and has worked as a journalist for 10 years.