Of all the evidence which police painstakingly gathered when they disinterred the body of murdered woman Keren Rowland from a pine plantation near Canberra airport 49 years ago, one crucial piece was missing.
It was a small, but vitally important item: a silver or gold Lynette bracelet.
Ms Rowland, then aged just 20, had bought the bracelet as a gift for a friend at the Royal Canberra Show and had been wearing it that same night of February 26, 1971, when she went missing.
Her body was found three months later.
The key question for police then, and now, is whether the bracelet was discarded at the crime scene, or whether her killer kept it as a "trophy" from the commission of that terrible crime all those years ago.
In the heavily wooded pine plantation between the Canberra airport precinct and the Air Disaster Memorial south east of the city, ACT police returned to the scene of the crime on Tuesday with metal detectors.
It was a long shot at finding that unrecovered piece of evidence that, with the benefit of modern forensics, may assist in shedding fresh light on a cold case which has baffled detectives for decades.
Detective Senior Constable Emma Beere said the Unsolved Homicide Team had been reviewing old case files and had been prompted to return to the crime scene after a person had come forward recently with fresh information.
The details of that information they are keeping to themselves but it was enough to push fresh energy into the investigation.
ACT police have been hamstrung in comprehensively reviewing the case because, for some inexplicable reason, all other key exhibits from the case - Ms Rowland's clothing, handbag and all its contents - were not carefully preserved for future review.
It was a critical policing error which these days would be unthinkable.
Ms Rowland disappeared on the night of the Canberra Show. She had gone to Civic to pick up her sister and take her to the Statesman Hotel, but her sister then decided to get a lift with her fiance. Ms Rowland followed them in her own car, a white Mini Morris 850 sedan.
She was reported missing to ACT police by family members about midnight that night after she didn't arrive at the party.
Her vehicle was later found on Parkes Way, Campbell, with no petrol in the tank.
"Keren was only 20 years old when she went missing and was five months pregnant," Detective Senior Constable Beere said.
"A full investigation was conducted at the time of the incident with strategies that were available to detectives, which mostly involved eye-witness accounts.
"Several persons of interest were identified but no charges were laid against any person.
"We've been speaking regularly with Keren's family and as we near the 50-year anniversary, we're looking for answers for them."
The detective said that those who first arrived on the scene were very surprised that Ms Rowland's body had not been found earlier as that area was frequented by many bushwalkers.
"An extensive search of the area was conducted over several days, and officers located items of clothing and her handbag. Keren's family reported she would have had a silver or gold bracelet and detectives at the time believed her killer may have taken it.
"The pine plantation has changed significantly since Keren's death. After consulting old maps to identify where exactly she was found, we're now searching the area with equipment that would not have been available in the 1970s.
"It has been a long-time but detectives don't close a case until it is solved, and that's why we're looking at other avenues of inquiry to try to figure out what may have happened to her."
Social history investigator and Queanbeyan freelance journalist Nichole Overall has delved as deeply as anyone into the Keren Rowland cold case.
Ms Overall has extensively examined as much evidence as she can find, spoken to family members and anyone connected with the case.
Her systematic, almost forensic review of the compelling case is detailed in her blog and her new podcast which goes live on Tuesday night.
"I've spent months and months sifting through the detail of this case and there are so many unanswered questions," Ms Overall said.
"I've managed to gain access to information which I think has surprised police. I'm happy to share it with them, of course, but I, too, would like them to share what they know.
"I doing this to honour Keren and her family. Her story deserves to be told accurately and transparently."
Anyone with information that could help police is urged to contact Crime Stoppers on 1800 333 000, or via the Crime Stoppers ACT website and quote reference 3290689. Information can be provided anonymously.