After being forced to leave his freezing works job in 1994 because of a chronic condition, he has been investigated four times for allegedly defrauding the Accident Compensation Commission (ACC), each time without prosecution.
When he mounted a campaign against officers and investigators who he believed searched his home without reason or proof, he was told by police that their officers had acted correctly.
"Right from day one I was treated like a criminal," he said.
The release of a report into the complaints by the Independent Police Conduct Authority to Mr Van Essen (42) on Friday left him feeling relieved and vindicated.
"The last month has been a huge nightmare of stress. I feel like a huge weight has lifted off my shoulders."
He has suffered from the stress of holding a very public campaign against the ACC fraud unit over the past two years, having to visit psychologists and doctors to help him cope.
He believes private investigator Peter Gibbons and Dunedin police officers have been "having a go" at him for years.
In September 2006, when Mr Gibbons, three police officers and an ACC examining officer searched Mr Van Essen's home, he was astounded the affidavit for the search warrant contained no apparent evidence supporting the search.
"They came to our house, they took away my father's stuff just after he had died. My mum and I asked them to respect my father's things but they just ignored us. They took all of my father's things and threw them on the floor in the middle of the room.
"They wonder why I was upset."
He said it had been a long battle to prove his innocence.
"It is bloody hard to prove your innocence when you are fighting the bureaucrats. They think that they are superior and we are nothing. They keep covering everything up and protecting their mates.
"My parents lived through the war in Europe; when the police and Mr Gibbons had taken everything away, my mother told me that it reminded her of the Nazi regime. They made me feel disempowered."
Last year, Mr Van Essen made public his concerns about an 80% "outcome-related quota" for investigations, required by ACC, which was included in an ACC contract with private investigation firm Mainland Information Consultants, the firm which had made inquiries in his case.
This resulted in ACC risk and assurance and fraud manager Ernst Le Roux calling the clause inappropriate and having it rewritten.
An independent review of the ACC fraud unit recommended several reforms, and said the unit had developed its own subculture which was not in step with ACC's overall approach as a responsive social insurance organisation.
The "success" of his complaint against Dunedin police in the IPCA report has now buoyed his confidence for the next battle - a hearing against the renewal of the private investigator licence of Mr Gibbons and his agents, starting on September 29.
Mr Van Essen is one of 16 people who have lodged objections to the renewal.
If the objections are fully upheld, Mr Gibbons and partner Graeme Scott will be unable to work as licensed investigators, effectively closing their company down.
Mr Van Essen is also considering filing for damages for stress suffered as a result of the proceedings.
When contacted yesterday, Mr Gibbons said he would wait until after the hearing to comment, but thought the public may find there was a "totally different side to the story".
