A group of supporters including former and current police officers will pay their respects in Awatoto on Friday at the spot where Kirsa Jensen was last seen, 40 years ago to the day.
The 14-year-old Napier schoolgirl went missing while riding her horse, Commodore, after school along the beachfront in Awatoto on September 1, 1983, sparking a large police investigation.
Police released a statement on Thursday and said the case remains one of New Zealand's "most enduring murder mysteries".
Kirsa's body has never been found and no one has ever been charged in relation to her disappearance.
Detective Sergeant Daryl Moore, who holds the file, said the case remains open.
He said police still receive information about the case from members of the public two to three times a year.
"Someone might think of something, or finally come forward after feeling like something doesn't sit right with them. We investigate all the information to see if it helps the case," Moore said.
Three years ago, the file, along with several other cold cases, were digitised by Eastern Police. Moore said the Investigation Management Tool (IMT) allows all the data in an investigation to be online and saved in one place for centralised access.
"We can then easily cross-reference new information to see if it is, in fact, new, or links to other information we already have."
Retired Assistant Commissioner Ian Holyoake led the inquiry, and he visits the memorial at the last place Kirsa was seen from time to time and looks around, still wondering if there's anything he missed.
Holyoake, along with Moore, Detective Inspector Ross Pinkham, who was the officer in charge of suspects and several other officers who worked on the case plan to meet at the memorial today, where years ago pōhutukawa trees were planted and a plaque was placed as a tribute to the teenager.
Holyoake said it's a case that still haunts him.
"I have never forgotten Kirsa Jensen, and I never will. I always live in hope that someone, someday will say something that will lead us to where she is, which would bring some relief and closure for the family," Holyoake said.
The case took a bizarre twist when one of the main suspects, local orchard worker John Russell, made a confession in 1985.
He later retracted the confession and told interviewer Paul Holmes he had been mentally ill.
Apparently tormented by his association with the events or the inquiry, he spent time in psychiatric institutions and took his own life in 1992.
It's understood Kirsa's mother, Robyn, would not make today's memorial gathering due to ill health.
In an RNZ interview in 2017, she said she will never stop looking for her daughter.
"A mother doesn't forget her child. I could no more forget Kirsa than fly to the moon. She's part of me and she's very important.
"A mother doesn't forget her baby. Until the day I die, I'll keep hoping. I'll never give up hope."
This story was originally published by the New Zealand Herald.