Thousands of people have taken ACC on and won after being denied compensation by the corporation.
Figures, released to the Herald under the Official Information Act, show 36,878 applications were lodged for an independent review of an ACC decision between 2012 and 2016 and more than 2700 district court appeals were made.
During that time, almost 16,000 independent reviews went in favour of ACC (43 per cent) while more than 6000 were decided in favour of the client (17 per cent). Another 14,500, or 39 per cent, were settled or withdrawn before the review but no information was given about how many were in favour of each.
More than 1900 district court decisions were issued with 1247 (64.5 per cent) upholding ACC's position.
Between 2001 and 2012 the number of reviews lodged each year rose from 4053 to 9281. Since then the number steadily dropped to 6518 in 2015 but rose slightly again last year to 6789.
ACC acting media adviser Chris Ritchie said the reasons for the increase leading up to 2012 included changes in policy to more closely align with legislation, a precedent-setting decision which had the effect of ceasing weekly compensation to a significant number of claims and announcements on ACC's financial stability.
Since then numbers had come down because ACC had begun to offer facilitation and mediation as options before going to a review and had focused on communicating with clients to help them understand how a decision had been reached, he said.
Barrister and lead author of 2017 report into ACC coverage Solving the Problem Warren Forster estimated between 200,000 and 300,000 were denied ACC coverage each year.
In response to the report, ACC chief executive Scott Pickering said ACC dealt with about 2 million claims every year. He estimated there were about 70,000 decisions to decline cover or entitlements each year but said within that number could be many decisions made for one client.
Of those about 6500 decisions were reviewed and 84 per cent were found in favour of ACC, he said.
Forster believed the difference in numbers was because ACC did not record each decision made for each client as a separate decline.
He was also skeptical of ACC's dispute resolution process.
"In my experience, and I've done 1000 odd reviews, people either give up because the barriers are so high to accessing justice or alternatively ACC rolls over. There are almost no cases where the person decides, actually, ACC's decision is right. I've probably had two cases where a person came along with a problem and there was nothing in it."
From the figures provided by ACC it was impossible to tell how many cases had been withdrawn or settled and in whose favour, he said.
The figures provided to the Herald found in the five years from 2012 only 43.3 per cent of reviews were found to be in favour of ACC. That meant the 39.4 per cent which were settled or withdrawn must also be counted in the corporation's favour to come close to the 84 per cent Pickering claimed it won.
Ritchie said ACC focused on resolving less complex cases before a formal hearing. A withdrawal was considered to be a favourable outcome because the corporation considered the issue to be resolved.
The percentage of reviews resolved pre-hearing had increased from about 34 per cent in 2009/10, to about 45 per cent, he said.
Forster said it was also a concern only 36,000 appeals were lodged when hundreds of thousands of decisions were declined.
"You're going to have a huge pool of people there who aren't actually engaging at all in the dispute resolution process and the most likely reason is they don't think it's going to work or they don't know how to do it."
A 2016 review carried out by Miriam Dean QC on behalf of ACC found the main issue for claimants was accessing and paying for legal advice and medical evidence.
"The barrier exists because of a considerable imbalance in the resources ACC can bring to bear on cases compared with those available to claimants," the report said.
Forester's report concluded the best way forward was the establishment of an independent personal injury commissioner who would "act dependably, independently, impartially and decisively to develop expertise, improve access to justice and improve public trust and confidence".
Not only was a commissioner needed for accountability but to help people to access legal and medical expertise.
The whole process took a massive toll on the claimant, he said.
"It doesn't just affect the person, it affects their families and communities too. It affects their relationships. Then there's the psychological effect, that's a big problem."
The appeal process
• ACC declines a claim for cover or entitlements.
• Lodge an internal ACC review of the decision.
• Lodge an independent statutory review usually run by FairWay.
• Appeal the findings in the district court.
One man's 11-year battle
Grant Rankin has been battling ACC for 11 years to no avail.
On March 15, 2006 the truck driver was standing on the trailer of his truck when he stepped backwards and fell about 1.5m, landing on his back.
The 60-year-old has not been able to work since because of severe lower back pain that he said had not subsided since the accident.
In the last 11 years Rankin and his wife have re-mortgaged their house to cover the $45,000 cost of numerous reviews and court appeals. He has become obese because he has not been able to exercise, developed Type 2 diabetes and was diagnosed with depression because of the stress of the ordeal.
"At the end of the day my back's buggered. I can't work - I've tried. I'm lucky if I can walk 100m down the road without being in pain," he said. "It's put a strain on my marriage... I trust very few people now. We've spent every waking moment and dollar we've got on lawyers.
"Life is just getting too hard. Way too hard."
ACC has constantly disputed the claim saying recent scans which showed osteoarthritis and nerve compression in his spine did not prove the accident was the cause of what was usually a degenerative issue.
After the accident Rankin went straight to his GP who said it looked like he had sprained his lumbar spine.
When the pain did not subside his doctor prescribed painkillers and sent him for an x-ray which showed bony projections on two vertebrae but no other damage.
Rankin said it was then that his doctor filled out an ACC claim form. He said repeated attempts to get hold of someone at the corporation who could help him over the next couple of years failed.
ACC said they did not receive a claim form until 2009 when Rankin's new GP filled out a backdated one and doctors' records showed only a few sporadic doctor's visits where back pain was raised.
A complaint made to the Health and Disability commissioner confirmed Rankin's suspicion that aspects of the clinical notes his doctor took were unwittingly omitted because of unusual power cuts at the clinic. The commissioner also found the notes kept by Rankin's doctor were slightly lacking in detail.
A musculoskeletal pain specialist who assessed Rankin four years after the accident said because Rankin had no pain beforehand, the damage in Rankin's spine was probably caused by the fall.
But the judge agreed that while theoretically it was possible the fall caused damage which had degenerated since, there was no evidence to prove it and that the degenerative condition was present in a significant percentage of people Rankin's age.
Coupled with the lack of treatment records in the three years after the accident, the judge found no reason to overturn ACC's ruling.
An ACC spokesman said in upholding ACC's treatment injury decision, the District Court noted that specialist opinions showed Rankin's symptoms arose from an a degenerative condition and treatment would not have altered this underlying condition.