Expert says murder-accused visited prime spot for disposing of body

An international expert on body disposal in homicide cases says an area visited by murder-accused David Benbow after a tactical police media statement was highly suitable for concealing a body.

Benbow, 54, is on trial in the High Court in Christchurch for murdering his childhood friend McGrath, 49, on May 22, 2017.

It’s alleged he shot McGrath with his .22 rifle after inviting him to his house at Candys Ave, Halswell, to help shift railway sleepers. The weapon and McGrath’s body have never been found.

McGrath and Benbow’s former partner Joanne Green had started a relationship, which Benbow found out about after his daughter saw the pair kissing.

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The Crown alleges Benbow made two unexplained trips to the Motukarara area near Lake Ellesmere, with proximity to the Halswell River, on August 6 and 7, 2017, after a police media release on August 3 about an expert’s involvement in the search.

Mark Harrison, a former Australian federal police commander and an expert in locating the bodies of missing people, said he was approached by Christchurch police in late July that year to help find McGrath.

He had suggested the investigation team make a tactical media statement saying police had consulted an international expert who would be assisting them find the most likely places where a body might be.

This had worked in the past to locate bodies because it could prompt an offender to revisit the site to move the body or body parts or do more to conceal it.

Harrison said an offender would commonly do frequent drive-bys “in the general vicinity to check on any police activity or media interest in order to maintain their confidence their concealment remains undetected”.

“This [Benbow carrying out drive-bys] would be wholly consistent with my casework experience, where the offender finds it irresistible to conduct daytime checks to maintain confidence in concealment.”

Harrison said in real life, burials in homicides were rare because of the difficulty involved. Disposal of a body was typically a nighttime activity and offenders were attracted to prominent markers that could be located in daylight.

Benbow had been tracked to an area that afforded ready vehicular access to the Halswell River. It could be inferred Benbow was familiar with the area, he said.

“In this case, Benbow had a significant window of time to conduct effective reconnaissance, and even through trial and error choose the most suitable location with the highest probability of concealment within a short distance of where he would have parked his vehicle near the access points to the Halswell River.”

Natural forces such as flushing and earthworks in the area in 2019 to create a wetland sanctuary may have removed any remains, the trial heard.

In cross-examination by defence counsel Marc Corlett, Harrison said he had not relied on other specialist experts in his evidence.

He had no formal qualifications in hydrology, surface water hydraulics or fluvial geomorphology – how rivers shape the land.

He had never visited the Halswell River or Lake Ellesmere, he conceded.

The method of using a tactical release was not the subject of scientific research, he said.

The trial continues.