Police brass have made a landmark decision to allow detectives to use a controversial DNA tool in a last-ditch attempt to solve the rape and murder of a young girl in 1980.

Law enforcement agencies overseas have had success comparing the DNA of unidentified suspects with genetic profiles uploaded to popular genealogy websites, most famously leading the FBI to catch the so-called “Golden State Killer”.

Detectives investigating the unsolved murder of Alicia O’Reilly wanted to try genetic genealogy testing to identify her killer, which has never been done before in New Zealand.

After an 18-month wait for expert advice to navigate the complex privacy and legal considerations, the Weekend Herald can reveal that Operation Sturbridge has now been granted permission to try the novel technique.

Detective Inspector Scott Beard broke the news to Alicia’s mother, Nancye O’Reilly, at a meeting in her Auckland home last month.

She was pleased there was now another avenue for the investigation to follow, but also keeping her expectations in check.

“I’m just trying to not get my hopes too high. In the past, there have been breakthroughs and it’s come to nothing,” O’Reilly said.

“I just have to keep a lid on [my emotions] really, otherwise it’s a huge disappointment.”

Barry O’Reilly, Alicia’s father who lives in Australia, was also optimistic of finally learning who killed his daughter. He also hoped the genealogy testing could solve other cold cases in New Zealand, and the public would support the police decision.

“We, as Alicia’s parents, are hoping this technology will find the person who viciously took Alicia’s life. Alicia can then be allowed to rest in peace.”

The decision to use the controversial DNA technique in the cold case investigation came soon after Nancye O’Reilly went public with her frustration at the 18-month delay by Police National Headquarters.

A spokesperson confirmed that New Zealand Police had approved the use of genetic genealogy testing, but the “next steps” were still being worked out.

“Police have carried out a thorough process to date to carry out due diligence on security, privacy, legal and ethical implications from this tool.

“Relevant considerations have since been through a governance process and it has been agreed this will now move to the next phase.

“Police are continuing to work through the next phases including work with external stakeholders. We will be in a position to comment further around next steps in due course.”

Nancye O'Reilly with a portrait of her youngest daughter Alicia. Photo / Alan Gibson

Alicia O’Reilly, 6, was found dead in her bed in the Auckland suburb of Avondale in August 1980, while her sister Juliet, 8, slept just metres away in the same room.

The horrendous crime shocked the country and hundreds of suspects were questioned in the homicide investigation, but Alicia’s killer was never found.

Detectives working on the case decades later believed that forensic evidence - hair and semen left by the killer - had been inexplicably destroyed during the original investigation.

But in a stunning twist three years ago, some unmarked samples were found in archives and scientists from ESR, the Crown research institute, were able to extract a full DNA profile of the perpetrator.

The startling breakthrough in August 2020 gave renewed hope to Alicia’s mother, Nancye O’Reilly, and the police inquiry team, Operation Sturbridge, that her killer would be identified.

But no DNA match has been found so far.

This is despite the genetic code being compared to hundreds of thousands of profiles, collected from criminals or crime scenes since the mid-1990s, held in DNA databanks in New Zealand and Australia.

Another 193 suspects have been ruled out so far after giving voluntary DNA samples.

So, after hitting a dead end, Operation Sturbridge requested permission from Police National Headquarters in November 2021 to try a novel avenue - investigative genetic genealogy.

This new technique has been made possible by the growth of databases overseas, such as FamilyTreeDNA, where individuals can research their heritage by uploading their DNA profile.

While investigations in New Zealand regularly compare DNA left at crime scenes with profiles held on the databanks, looking for either a direct match or a close relative, genetic genealogy allows police to cast the net much wider.

Tens of millions of people worldwide have shared their profiles on these popular websites, meaning the likelihood of law enforcement finding a genetic relative to a suspect has vastly improved.

Detectives can then use the results of a genetic genealogy search alongside other records to construct a family tree, to then identify the most likely suspects for further investigation.

The technique has been used with dramatic success to solve cold cases overseas, most notably the capture of the “Golden State Killer” who committed at least 13 murders and 51 rapes between 1974 and 1986.

While the potential of genetic genealogy for criminal investigations is obvious, the technique is not without controversy; not least the concerns of private citizens voluntarily giving their DNA to a private company for one purpose, only for the state to use it for a very different one.

Adding another layer of complexity to whether genetic genealogy can be used to find Alicia O’Reilly’s killer, is that the current law governing the use of DNA in criminal investigations needs to be overhauled.

A review by the Law Commission, published in November 2020, found the Criminal Investigations (Bodily Samples) Act was “no longer fit for purpose” and made 193 recommendations for change.

Given the significant privacy concerns around turning users of ancestry websites into unwitting “genetic informants” against their relatives, the Law Commission said any new legislation needed appropriate safeguards for police to use genetic genealogy.

“Our view is that genetic genealogy searching should be used as a last resort and only in relation to offending that, when considered in its full context, is sufficiently serious to warrant the use of such an intrusive investigative technique.”

While the Labour government accepted the Law Commission findings in early 2021, no progress has been made on changing the law.

• Anyone with information for the police can call 105 and quote either Operation Sturbridge or the case file number 800816/3613.

Jared Savage is an award-winning journalist who covers crime and justice issues, with a particular interest in organised crime. He joined the Herald in 2006, and is the author of Gangland.