A jury has retired to consider its verdict in the retrial of former prison guard David Benbow, accused of murdering his childhood friend Michael McGrath.

Benbow, 54, denies killing Michael McGrath in the Christchurch suburb of Halswell in 2017.

The Crown alleges Benbow murdered the 49-year-old after finding out he was in a relationship with his former 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 says 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 says McGrath never showed up and that Benbow is in no better position than anyone to say what happened to him.

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

Benbow pleaded not guilty during a seven-week trial at the High Court in Christchurch earlier this year. No verdict was reached.

On Monday, the jury retired to consider its verdict after hearing a summary of the case by Justice Jonathan Eaton.

Last Wednesday, Crown prosecutor Barnaby Hawes gave his closing address to the jury.

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He began by saying the Crown case was that the trial was one in which “human nature sits at the very heart”.

“The Crown says through a process of judgment, logic, common sense and knowledge of human nature, that the plight of Michael McGrath can be determined by you.

“By working carefully and clinically through the evidence that you’ve heard over the previous weeks, the Crown says that what you’ve been left with is the single reasonable explanation for the disappearance of Michael McGrath, and that is that the defendant David Benbow murdered him.”

Hawes acknowledged it was a circumstantial case, with no body to examine, no murder weapon, no DNA and no confessions.

However, he said the case against Benbow was “compelling and it’s decisive”.

McGrath was not the sort of person to just simply walk away from his life, from his family and friends.

“He was a reliable and dependable man, a creature of habit... a person who lived his whole life in Halswell.”

Crown prosecutors Claire Boshier (left) and Barnaby Hawes. Photo / Iain McGregor

McGrath had “difficult times”, but by May 2017 those days were behind him and he displayed none of the risk factors associated with suicide.

“He was genuinely happy... he was upbeat, the Michael McGrath of old in good spirits,” he said.

“He was not in any way suicidal.”

News of McGrath’s new relationship with Joanna Green, Benbow’s ex-partner and the mother of their two children, had reached the one person who did have cause to be unhappy about it, Hawes said.

“In an exhaustive search into Mr McGrath’s life, the one, the single source of conflict... was from David Benbow,” he said.

“It was David Benbow who said that Michael McGrath had stabbed him in the back; it was David Benbow who said he wanted to annihilate Mike. It was David Benbow whose world came crashing down when he learnt Joanna Green had moved on from David to Michael McGrath.”

How Benbow reacted to his break-up was in “stark comparison” to how he reacted when he heard Green was dating McGrath.

A week before McGrath disappeared, Benbow turned up at his Checketts Ave home three times, first to ask for assistance in moving items around his section, then to invite him for dinner, and then on May 21 to make an appointment for McGrath to visit him at 9am on May 22 to move some railway sleepers.

Benbow would later say McGrath never showed up at his home that morning. However, Hawes cited witnesses who spoke at the trial who said “he was a man who would do what he said he was going to do”.

David Benbow is accused of murdering his childhood friend Michael McGrath. Photo / Iain McGregor

He asked the jury to “think long and hard” about Benbow’s missing .22 rifle.

“A firearm is not like a different type of lethal weapon. It comes with specific legal obligations. He had one firearm, according to those who knew him, he was conscientious about it, this cannot simply be brushed over... there is no adequate explanation as to what might’ve happened to that firearm other than Mr Benbow disposed of it himself.”

Hawes mentioned how Benbow did not contact McGrath’s family nor did he volunteer time to help search for him.

“It’s almost as if he knows searching is pointless,” Hawes said.

“Not interacting with Michael McGrath’s family is insulating himself from what he’s done.

“This is a man and family he’s known for his entire life... his response to the disappearance of this man is to do very little other than the absolute bare minimum.”

He said it was not the Crown’s case that this was the “perfect murder”.

Justice Jonathan Eaton. Photo / Iain McGregor

“Mr Benbow is a careful and deliberate man but everyone makes mistakes... He’s hidden his body well and utilised an outdoor scene to his advantage, kept things very simple and spoken to nobody about it. Nevertheless, I suggest the facts speak for themselves and prove murder beyond reasonable doubt.”

To find the charge of murder proven, the Crown needed to prove five fundamental matters, Hawes said - that McGrath is dead, that he did not take his life, he had not died in an accident, that Benbow caused his death and that he intended to kill McGrath.

Hawes said McGrath’s disappearance was not explained by anything other than foul play.

“Mr Benbow may not previously have been a violent man. He may have been a good father, a teddy bear, but this is not inconsistent with him also having murdered Mr McGrath in the unique circumstances he found himself in in May 2017.”

He told the jury that if they find a set of individually reliable facts to not look at them individually, but in combination.

“You need to look at the circumstantial case in the other direction too, that is if Mr Benbow has nothing to do with the disappearance of Michael McGrath, then that list of reliable facts is a list of very unfortunate coincidences for Mr Benbow in the context of a missing person’s homicide investigation.

“Has Mr Benbow just been unlucky to have significant evidence suggesting his involvement in a homicide, or is it that he is involved?”

“That’s not like lightning striking twice in the same place. In the context of this case, this is lightning striking the same place over and over again.”

David Benbow's lead defence lawyer Kirsten Gray. Photo / Iain McGregor

Benbow’s lead defence counsel, Kirsten Gray, then closed their case to the jury.

She said the Crown’s case was based on a “theory”.

“A theory that was first thought up by Joanna Green, the theory that Mr Benbow had done something to Mr McGrath. And it’s a theory that is desperately searching for evidence,” she said.

“In this case, you’re not here to solve the disappearance of Mr McGrath. You are here to determine beyond reasonable doubt whether or not the Crown has proven its case against Mr Benbow.”

Gray referred to the Crown suggesting the case was like strands of a rope, that once they come together make a rope so strong that you can rely on it beyond reasonable doubt.

“Be very cautious about that submission. If you look at the strands of the rope in detail you might be left scratching your head. The strength of the rope, members of the jury, is your domain, it’s for you to decide. But you need to ask yourselves at the outset do you accept that this is a rope, or, as I suggest, is it just a pile of tattered threads, a house of cards not capable of withstanding any serious probing.”

She said the jury had more evidence that police focused only on Benbow than evidence of anything else, citing the 8000 hours they spent searching a dump compared to the 800 hours looking for McGrath.

“This doesn’t amount to a rope and it certainly doesn’t get you to the high standard of beyond reasonable doubt.

“In my submission, the Crown case is a house of cards built on shaky foundations which, if you give it any real probing, will simply fall over - and if you drill into what is being alleged, then things don’t make sense and the improbability of their entire case is glaringly obvious.”

She put the evidence into three categories - evidence of nothing, which she called “red flag evidence”, and “lens evidence”, that could be viewed either way, depending on what lens you look through, and actual evidence that the jury could use and rely on.

In relation to Benbow not offering to help search for McGrath, Gray said at first glance that may look suspicious, but in another view it may seem like “sensible self-preservation”.

“How welcome do you think Mr Benbow would’ve been joining the search for McGrath?... after all that happened on the Tuesday night... he would not have been welcome at all. By this point, Ms Green had pointed the finger well and truly at him. He knew the McGrath family suspected he was involved, he knew the type of reception he would get if he tried to assist.”

Gray said there was “very little” in the case that even began to resemble real evidence.

“If you even begin to scratch the surface of this evidence, it becomes clear it doesn’t get you anywhere near establishing that Mr Benbow was involved in a homicide.”

She cited the lack of forensic evidence, given the Crown had at least three crime scenes - Benbow’s home, his car and McGrath’s home.

“No blood, no DNA, nothing of any forensic interest.”

Benbow, Gray said, did not have a motive nor the means or opportunity to commit a murder.

She then summarised each of the three key people in the case - McGrath, Benbow and Green.

McGrath was not “uncomplicated” as the Crown suggested, but a “complex individual,” she said.

Benbow was a good father who loved his daughters. He worked hard, but he was not the best partner, Gray conceded.

“He took Joanna Green for granted, let his relationship slide, he was focused on finishing the house and brought his work home.”

He was not, however, a violent man and had no previous convictions.

Benbow and Green’s break-up was “bog standard”, a “mundane, pedestrian break-up”.

“It’s a relationship which needed to end on any view of it.”

Gray warned the jury to be careful when considering Green’s evidence, who she called an “unreliable narrator”.

She also asked them to take care with what she said about her relationship with McGrath, given she was the only one who told the jury what McGrath was saying in the relationship.

Gray said rather than the case being about lightning striking over and over, it was more of a “chain reaction” that started with Green.

“A tidal wave started by Joanna Green and then took on a life of its own.”

To believe Benbow had the capacity to commit the “perfect murder” was “farcical”, she said.

Gray said the police had “tunnel vision”, and worked off a “suspect-driven theory”.

She concluded by telling the jury this was a case with “no body, there is no weapon, absolutely nothing of forensic evidence implicating Mr Benbow.”

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.