LE have experience searching areas of water around Chch
Court hears murder accused could have hidden body in river bank
I closely followed the trial of DB accused of murdering friend Michael McGrath...following is intel provided by an Australian university professor and private consultant in police intelligence and geo-forensics – "the science of search" when giving evidence at the trial
Mark Harrison, a former Australia Federal Police head of intelligence, was first contacted by New Zealand Police on June 12, 2017, for help in the "sudden and unexpected disappearance" of McGrath
In homicides, water features as most the preferred method of disposal, where it is accessible and follows the "least effort principle" of disposal, Harrison told the court.
While movies often show criminals digging graves for victims’ bodies, in real life it is rare due to the effort required, he said.
A body disposal area is usually known to the offender, Harrison said, easy to access, has clear, permanent identifiable features or markers, like a large conspicuous boulder, and has a good chance of not being seen by any potential witnesses.
After looking at the case, Harrison concluded: "I am therefore of the opinion that the Halswell River and wetlands would’ve afforded Benbow a highly-suitable location to conceal and dispose of McGrath."
Benbow could have parked close to the river and carried McGrath’s body, perhaps using a tarpaulin or other wrapping, the witness 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 could’ve parked his vehicle on any of the aforementioned access points to the Halswell River," he said.
Digging a shelf into the side of the riverbank would’ve been easier than digging downwards, Harrison said.
But given the changeable, dynamic nature of the river, if McGrath’s body had been there, "his remains may have already been removed either through natural forces, flushing, or those undertaken by the land management processes."
A "flushing effect" was a highly-likely scenario, Harrison said, meaning a body buried into a riverbank could have been washed into the river, potentially out to Lake Ellesmere which the river feeds into, and even further out to the open ocean.
A 2km section of the river was searched by NZ Police, using dogs, divers and search experts, between July 9 and 13 2017, the court heard.
Harrison said it would’ve been "extremely challenging work" given its dynamic, changing nature.
"While further searches could be considered they would require careful planning and resourcing due to the complex and dynamic nature of the search area."
In August 2017, Harrison advised Operation Renovation detectives to release a "tactical" media statement which said police were working with an international search expert and had identified geographical areas of interest in the greater Christchurch area that specialist search teams would focus on.
