Benbow, 54, denies killing Michael McGrath in the Christchurch suburb of Halswell in 2017.
He pleaded not guilty during a seven-week trial at the High Court in Christchurch earlier this year. No verdict was reached.
A retrial began at the High Court in Christchurch this week.
One of Benbow’s lawyers, Kathy Basire, gave a brief outline to the jury of the defence’s case. She said the outline would only be short and that the jury would hear more from the defence once it opens its case after the Crown has finished calling its evidence.
She said the defence case was "simple".
"Michael McGrath did not show up to David Benbow’s house on the morning of 22nd May 2017 and David Benbow has no better idea what happened to Michael McGrath than you or I.
"To be clear it’s the defence’s position that Michael McGrath is missing, there’s a number of reasons why he could be missing suicide, accident, deliberately doesn’t want to be found or the subject of foul play by person’s unknown."
Benbow did not have to prove anything to the jury at the trial, and the defence did not have to prove what happened to McGrath.
"Nor is it your job to solve the mystery of where Mr McGrath is, your only job is to consider whether the Crown has proved its case of murder against Mr Benbow."
Basire suggested the jury should pay particular attention to what the police "did or didn’t know" about McGrath’s life.
"Despite the finger of blame being pointed at Mr Benbow by his former partner on the night of 23rd May, that’s the day after Michael McGrath is believed to have gone missing, despite the police going to his property that very night on 23 May and the next day and other days that week and the police seizing his property searching for 10 days.
"Despite extensive examination of Michael McGrath’s property and both men’s cars, the police have not found any evidence that a crime has been committed. No sign of disturbance, no forensic evidence, and no evidence of a clean-up of forensic evidence. There’s no body, there’s no evidence of body disposal, no murder weapon, no eye witness to an assault or murder."
Basire said the jury would hear Benbow had no criminal convictions and had "worked hard all his life".
Around the time of McGrath’s disappearance, Benbow was on sick leave, he was depressed, had low mood and wasn’t sleeping much or eating well.
Benbow was seeing his doctor regularly, joined a gym, was also seeing a counsellor and doing small jobs around his section in preparation for the "inevitable sale" of the property.
His main focus over this time in May 2017 was his access to his children.
Basire said Benbow was "far from planning the perfect murder".
"He was living day to day just getting by."
She said Benbow "adored his children", and would do nothing to jeopardise their future or his.
Basire then said the police in their focus on Benbow being responsible for what happened to McGrath developed "tunnel vision and have no doubt missed vital clues as to what happened to Michael McGrath".
"We know by focusing on Mr Benbow they didn’t find Michael McGrath," she said.
She added: "absence of evidence is not evidence itself".
‘Means, motive and opportunity merged into murder’
Crown prosecutor Claire Boshier gave her opening to the jury on Tuesday.
She began by saying Benbow told his counsellor he would like to "annihilate" McGrath 20 days before he disappeared.
After his disappearance, he allegedly told a friend, "I don’t give a f*** what happened to him - it just teaches you not to introduce your partner or wife to another man."
The ‘annihilate’ comments were made after Benbow’s daughter told him she saw his ex-partner, Joanna Green, kissing McGrath.
Boshier said Benbow told a friend he was "very pissed off", and another friend said he appeared "very angry and distressed".
The Crown case was that Benbow planned to kill McGrath, and did so on May 22 at his home on Candy’s Rd, Halswell. They allege he then disposed of his body in a way that meant it had never been found.
The motive, the Crown said, arose out of Benbow learning of the relationship between Green and McGrath, who he had known since they were children.
While the Crown case consisted of many different strands of circumstantial evidence that may seem insignificant, when woven together, they became "much more important", she said.
"When you put them all together, you find a series of otherwise inexplicable coincidences", Boshier said.
"The only reasonable explanation for the disappearance of Michael McGrath is murder at the hands of David Benbow."
"Mr Benbow is the only person who had the motive, the means and the opportunity to murder Mr McGrath."
To prove the charge of murder, the Crown needed to prove he was dead, it was not an intentional disappearance and he had not committed suicide.
Boshier then ran the jury through a number of different strands of evidence the Crown case was built on.
She began with the intensity of the searches around the Halswell area for McGrath. She said if he had died in some other way that wasn’t murder by Benbow, he likely would’ve been found.
McGrath’s car and bike, which were his only methods of transport, were found at his home.
At the time of his disappearance, McGrath’s mental state meant he was at a "low risk" of suicide. He had depression in the past, with a pain disorder in his leg, but in May 2017 he was in a new relationship with Green, who he had fancied for years. He told Green they could be "soulmates".
"His friends and family will tell you he had everything to live for," Boshier said.
"He was making plans for the future."
McGrath was also "highly reliable", and if he said he would be somewhere, he would be, Boshier said.
Green told Benbow in February 2017 that their relationship was over, and on March 3, 2017, she moved out with the help of McGrath and another friend.
Boshier said Benbow was "furious" about the break-up, and told Green’s sister he had "lost everything".
After finishing a large deck for Benbow over the summer of 2016 and 2017, McGrath distanced himself from Benbow. There was only one phone call between the two men in March 2017.
However, 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.
Boshier said the Crown alleges moving the sleepers was a "ruse" to lure McGrath.
When police spoke to Benbow on May 23 at his home, he did not mention the sleepers. It wasn’t until the next day that he pointed them out on the lawn. When a police officer moved them the following day, there was no dead grass on the lawn.
Benbow had also been described as "obsessional" about CCTV cameras at his home. She said the cameras were turned off about a week before McGrath’s disappearance.
Boshier then ran the jury through means, motive and opportunity.
"Mr Benbow is the only person with all three."
His firearm was missing, and his home on Candy’s Rd was in a secluded area with high hedges. His motive, she alleged, was not so much the break-up, but the knowledge Green was moving on with an old friend who was "soon stepping into his shoes in all manner of ways".
She also said he had the opportunity, as the Crown said Benbow was the last person to see McGrath alive at 9am on May 22.
"Where means, motive and opportunity merged into murder."
At various points on May 22, Benbow was seen wearing a baggy blue woolen jersey. However, the jersey had not been found.
Some blue fibres were found in the driver’s seat of McGrath’s car. It was not possible to test the fibres against the jersey.
Blue fibres were also seen on the driver’s seat of Benbow’s Toyota Camry. The tests said the fibres could not be excluded as coming from the same source.
Two months after McGrath went missing, police were granted a surveillance device warrant, meaning they were able to intercept his phone calls and text messages and place a covert tracking device on his car.
On August 4, 2017, after receiving advice from a geoforensic search specialist, police released a tactical media release detailing that an international expert had been working with police in the search for McGrath.
The release detailed that police had identified geographical areas of interest in the greater Christchurch area and that specialist search teams would be brought in to search those areas.
The following day, Benbow received a call from a friend. In the call, which was intercepted, the friend told Benbow about media coverage of the press release.
Benbow told his friend: "They’re leaving no stone unturned, so good."
During the time police were tracking Benbow’s car, they logged a daily summary of his movements to identify any "unusual" trips.
Boshier said there were two trips that stood out, on August 6 and 7.
About 8pm on August 6, he drove to a rural address in Motukarara and stopped for more than two minutes.
On the following morning, he allegedly drove to the same area and stopped at two other spots.
They were the only times he went to that area in five months of surveillance, the Crown claimed.
Boshier posited whether Benbow was checking the area to see if police had gone there searching for the body.
"Whatever the reason, it was unusual and unrepeated behaviour of Mr Benbow … [which] came close in time to the tactical release."
Police searched sections of the Halswell River and surrounding wetlands but found nothing, with Boshier likening it to finding a "needle in a haystack".
The trial, before Justice Jonathan Eaton, continues and is expected to call around 120 witnesses and last up to eight weeks.
