Tracing the specks of biological matter left by a man last seen in Auckland well over a decade ago is hard enough when there's an obvious starting point.
Yet David Hart - the past owner of the Mount Eden boarding house where human remains were found January 31 - did not carve a typical route through Kiwi life.
A gold prospector on the West Coast in the 80s and landlord for a motley assortment of ex-criminals and drifters in inner city Auckland before he disappeared in the 2000s, Hart's life was unconventional to say the least.
The small markers of our genetic makeup that are recorded by dentists and doctors, and that live on in our relatives, are seemingly absent in Hart's past.
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Police forensics this week continued their examination of the skull and bones, and the concrete slab they were encased in the backyard of 3 Marlborough St on January 31.
A police contact told the Herald on Sunday that Hart is the obvious first candidate to be the remains, after disappearing without trace at least 10 years ago.
The source said the bones were thought to belong to an adult.
Police would not be drawn this week on the status of the investigation.
However, following the transportation of the remains to the mortuary on February 4, Acting Inspector Glenn Baldwin said the post mortem would be "meticulous and challenging work".
Simply obtaining a DNA profile from the body "may take a week or two", Baldwin said.
"But identification can only occur if police and ESR have a comparative DNA sample that the deceased's DNA can be compared to."
ESR [the Institute of Environmental Science and Research] is the lead forensic science agency in New Zealand. A spokesman said he could not comment on the identification process because ESR may be asked to help in the case.
However, leading forensic pathologist Dr David Ranson of the Victorian Institute of Forensic Medicine says not finding a comparative DNA sample could be the sticking point that may draw out the identification of the Mount Eden bones into months or even years.
"Look, it just totally depends on the circumstances. Some information comes to light and the whole thing may be sorted out in a couple of weeks. Other times nobody comes forward and you have the person in your fridge for years.
"And that's certainly been our experience, we've certainly had those situations where a deceased person has been in the fridge for many years."
So - setting aside a benevolent tip from the public to police on how and why those bones in the Marlborough St backyard got there - what are the most likely breakthroughs?
There are four classes of forensic expert who typically look at remains.
Forensic pathologists focus on determining the cause of death, forensic odontologist look at dental identifiers, forensic anthropologists examine the skeleton, and forensic scientists focus on the DNA and molecular biology of the remains.
At the outset, it doesn't get much better than a teeth record, says Ranson.
"It is the forensic odontologist, or forensic dentists, who do the work on identification via teeth.
"Now if you've got teeth it's a very powerful investigative tool, particularly if you can find original dental records and they use these complex matching systems.
"They can sometimes look at dental x-rays and compare that with bone markings and dental features and so on."
Ranson says the job of forensic pathologists and scientists of extracting DNA from the bones is one of the first steps in the process of identification.
"It isn't always easy to get DNA extracted from the skeletal remains but sometimes it is. It would depend a little bit on the condition the bones were in, and what the body was subjected to after death as to how recoverable the DNA is.
"But often you can get DNA from quite damaged remains. So in a general sense - 10 years on - I would be reasonably hopeful that they get DNA samples."
The next necessary step is finding a comparative DNA sample from the past.
This is a difficult task for a rotating set of Mount Eden boarders from 10, 20, 30 years ago who lived such superficially rootless lives.
"The biggest issue for DNA in all these things is getting a reference sample," Ranson says.
"So for the person they're suspecting it is, if there isn't any other access to their DNA from their life then DNA is not going to be of great importance.
"Unless they've got parents or siblings or children to do one of those genealogical type DNA approaches.
"Then you've just got DNA there, it doesn't tell you anything."
A possible source for a DNA reference could be something as simple as an object someone owned such as a book or a piece of clothing.
If a person was born post late-1960s (which Hart wasn't - he was in his 70s when he disappeared during the 2000s) then there may be a Guthrie card on record - which is a blood stain from a neonatal heel prick of newborns.
This could be tracked down if forensics can determine where a candidate for the bones may have been born.
Modern genealogy sites may also be able to create a lead for a relative of the DNA extracted from the Mount Eden bones.
"New genealogy sites offer some features. You can go back to cousins in some cases and try and get links," Ranson says.
"It can be a less direct relative. I think you can go out to some cousins. It does provide some useful investigative leads."
The forensic anthropologist will examine the skeletal remains specifically.
GP medical records are a helpful score for this.
"Let's say perhaps he saw his GP for gout or something like that and there is evidence of gout [in the bones], then you'd say we're now starting to hone in and you start looking at other things to start to get that further level of focus of identification," Ranson says.
"They'll look for evidence of an old fracture. Did the person have a fractured ankle in the past? Did they have some sort of hip replacement or some sort of procedure that gives you a local identifier?
"If this person's had a hip replacement then surely you're going to the relevant hospital in the area and say, 'Here's the serial number of this hip prosthesis, let's work our way back'.
"We've had success with that in the past. So all these things are very dependent on what's actually there."
An x-ray or radiograph of a person would also be an obvious reference to compare skeletal remains to, however Ranson says these were often destroyed over the years.
Aside from the direct correlation of past injuries identified in the skeletal remains to medical records obtained of Hart, or any other of the Marlborough St boarders, a simple picture of a person can yield some useful results via CT scans.
"Say you've got the body's skull. There are things they can do with CT scans of skulls and modelling it on photos. From the photographs you can see certain facial features. Maybe that can be mirrored onto a skull."
However, Ranson describes this technology as a "very soft piece of science" which is good at excluding people as the identity of the remains, but not good an conclusively saying they belong to someone.
The Herald on Sunday has been unable to uncover a photo of Hart in investigating the history of the Marlborough St boarding house, however police have been showing various people they speak to in their investigation - in Auckland and in Blackball where Hart had a home - a photo of a man with a goatee.
The concrete slab which the remains were encased in is necessary to look at, but Ranson says it's likely to have degraded any biological evidence contained in it.
"If fluids get into concrete and then dries out, that might preserve some DNA.
"But concrete's not nice stuff chemically. It's quite nasty stuff. So it's likely to break things down quite a bit."
But despite all these modern forensic techniques to direct police to the identity of the bones, Ranson says the roving life of Hart and others in the house makes it particularly difficult.
orensics have played a part in identifying human remains - and the cause of death - in a number of high profile cases.
The body of mother-of-one Carmen Thomas was found inside containers of concrete buried in the Waitakere Ranges in West Auckland in 2010, almost four months after she was last seen.
Her ex-partner, Brad Callaghan, was sentenced to life in prison in 2012 for murdering her by repeatedly hitting her on the head with a baseball bat when told he was not the father of their son.
A CSI-style show, Forensics NZ, revealed how blood-spatter analysis on Thomas' washing machine proved the force and the impact of the weapon.
Forensic testing was also done on the plastic of a wheelie bin missing from Thomas' flat and which was found at Callaghan's house with the serial number gouged out. It was believed this was used to transport her body and the testing enabled the serial number to be revealed and confirmed which address the bin belonged to.
In 2014, the bodies of Pakeeza Yusuf and her daughter, Juwairiyah "Jojo" Kalim, 3, were found buried under the Takapuna overbridge in Auckland's North Shore. The Crown said they were killed at the end of 2006 or early 2007 but they weren't reported missing until 2013.
Yusuf's boyfriend Kamal Reddy was found guilty of their murders in 2016 after a six month-long undercover operation which led to him admitting what he'd done and leading an undercover officer to the burial site.
In December 2018, the body of missing British backpacker Grace Millane was found in a suitcase in the Waitākere Ranges after days of appeals from police and her family.
In November last year, a jury heard from forensic scientist Dianne Crenfeldt who said DNA tests strongly suggested that spots of blood found on the accused's fridge in his apartment belonged to Millane.
Last year, Malcolm Rewa, after a third trial, was found guilty of murdering Susan Burdett in her South Auckland home in 1992.
Teina Pora had been wrongfully convicted for the crime and spent 20 years in jail. The Privy Council finally quashed Pora's convictions in 2015.
Rewa's DNA was found at the scene - and in the second trial he was found guilty of her rape. But the first two juries failed to reach a unanimous verdict on the murder charge.
While David Hart may be police's obvious first candidate for the Marlborough St bones, speculation they belong to various high profile Auckland missing persons cases has swirled.
Two notorious cases that were posed to a Herald police contact as possibilities were 17-year-old Joanne Chatfield who disappeared November 19, 1988, and John Tam, who vanished in November 1996.
Police are no closer to knowing what happened to the 17-year-old, who was last seen walking up Princes St as she left a function at Auckland University just before midnight on November 18, 1988.
Since then, there has been much speculation over what happened to Ms Chatfield, including rumours that she had run away or moved to Australia, but nothing has ever been confirmed.
Yet, the police source ruled out Chatfield as "definitely not" the Mount Eden remains, noting they were thought to belong to an adult.
No such clarity was provided by the police contact around John Tam - a 60-year-old retired market gardener, was reported missing from his family's home and market gardens in Tidal Rd, Māngere, in November 1996.
After an extensive search, police found no sign of him. In November 2004 police took the unusual step of reporting his death to the coroner without a body or any idea of how he died.
If a missing person police report was made on one of the candidates for the Mount Eden bones then that again could direct the search. But at least for Hart, police confirmed no such missing report was ever made.
Ranson says all these factors make a case such as the Mount Eden bones "very difficult for police".
"I mean it sounds like the police have got a long way to go here because they've got to check pretty much every lodger who's been in that place and any enemies they had.
"I would have thought unless someone comes forward and says, 'When he disappeared I always felt Frank, who was in the house at the time, was a suspicious character blah blah' then they get a particular immediate lead.
"Unless something like that comes up I would have thought we were up to many months or years."