An investigation into a crash near Kerikeri which claimed two lives and left an American tourist facing a string of charges was blighted by "serious deficiencies", a report has found.
In April 2018, a Subaru station wagon heading south on State Highway 10 and a Toyota camper van travelling north collided head-on near the bottom of Bulls Gorge.
The crash claimed the lives of the driver and front-seat passenger in the Subaru, both from Northland's Matauri Bay, while two backseat passengers were seriously injured.
A passenger in the van sustained a broken wrist while the driver, a 21-year-old man on holiday from the US, had only minor injuries.
The van driver was charged hours later with five counts of careless driving causing injury or death, which was escalated within days to aggravated careless driving causing injury or death.
The survivors from the station wagon told police the van was on the wrong side of the road when the two vehicles collided.
However, all charges against the van driver were dismissed when the survivors changed their statements a few days before the case was due to go to trial.
In their new statements, they said the crash had been caused by their friend, the driver of the Subaru.
The defence lawyer's argument was that he was suicidal and deliberately drove into the Toyota's path.
A report released on Thursday by the Independent Police Conduct Authority (IPCA) has criticised the police investigation, which it said relied too much on the survivors' initial statements.
It also found the crash investigation was not sufficiently thorough given the potential for criminal charges, because the crash analyst regarded the cause as "clear cut" and assumed the tourist had been on the wrong side of the road when the vehicles collided.
The IPCA found the first officers on the scene correctly prioritised giving first aid, but should have called for extra, more experienced staff, including members of the Criminal Investigation Branch (CIB).
The decision to charge the van driver quickly was appropriate, given the risk he could have left the country, but there was not enough evidence to elevate the charges a few days later.
The IPCA acknowledged the resourcing constraints faced by police working in rural areas such as Northland, including limited access to training and supervision.
"However, despite the inherent constraints of working in a rural station, the onus was on the officer in charge of the investigation to seek assistance when he recognised the job was beyond his capabilities," the report stated.
While the two people who died in the crash were not named in the report, they were formally named at the time as Yvarn Tepania, 24, who was the driver, and James Hamiora, 26.
Toxicology evidence showed Tepania had methamphetamine and five times the legal limit of alcohol in his bloodstream.
The driver of the van was US citizen Reiss Berger, who was 21 at the time.
Northland police said they accepted the IPCA's findings.
Acting Northland district commander Inspector Dion Bennett said police had since changed the way they investigate serious crashes.
That includes establishing detective sergeant and Criminal Investigation Branch investigator roles within the Road Policing Group, developing a guide for staff interviewing people involved in crashes, providing serious crash training, increasing staff recruited into the area and improving rostering.
Northland's serious crash investigation policy, updated in mid- 2022, now required CIB involvement in any fatal crash investigation.
"We understand the impact these tragic events have had on the families involved and accept responsibility for our role in this situation," Bennett said.
The IPCA report states that the authority started its investigation after a media outlet published a report on the case and the dismissal of the charges against Berger.
Berger had hired former Northland MP Mike Sabin, now a private investigator, who unearthed the evidence clearing him of wrongdoing, including the new statements from the survivors.