Today, Justice Timothy Brewer released his decision, dismissing Opai's court action against the police after a week-long trial in early July.
Opai, who began working for police in 2005 and become a file management support officer, alleged Culpan's comments were false, tarnished her reputation, ostracised her from colleagues, and prevented promotion.
Opai's counsel, Neville Woods, said during the hearing his client also suffered physical and emotional stress-related issues as a result of the dispute.
The police's defence, led by Matthew McClelland QC, said the remarks were published on occasions of qualified privilege and were not serious enough to engage in a defamation proceeding.
Opai took particular exception to one passage of the draft performance appraisal by Culpan.
Although the overall nature of the performance appraisal was positive, he said her "sense of responsibility can be misdirected and be viewed by other[s] as malevolence, or ill will".
Culpan also wrote the internal briefing paper as part of a staffing review.
In it, Opai claimed, several parts which outlined differing management styles causing poor communication and disruption were defamatory.
"The root cause of this tension appears to have been through a power struggle by some supervisors, a void leadership and management from the previous O/C Station, and a truncated investigation into two employment complaints," the paper reads.
Culpan's complaint form came after apparent discrepancies were discovered in the time sheets for Opai and her staff.
The manager was concerned his staff were leaving work early but were still claiming a full day's pay.
He titled his report: "Melissa Opai: Breach of the Code of Conduct".
"It would appear that these issues have reached a tipping point," Culpan wrote.
"It is my opinion that if the staff named in the email/complaint have left early without correctly filling out time sheets, it will have been sanctioned by Miss Opai although I have not traversed this point with those identified.
"I believe these actions fall under the general headings of Honesty and Integrity and dependent upon interview with Miss Opai, may be viewed as misconduct in that they represent repeated absence from duty or place of work without proper reason or authorisation."
Opai alleged the report gave the impression she was dishonest, a hypocrite, lacked integrity, and there were grounds justifying an employment inquiry.
She also took exception to Culpan's diary entries which noted Opai's performance and were handed to his successor in 2014.
One entry described a complaint Opai made as an attempt to "scuttle [two persons'] police enrolments".
The other was about timekeeping complaints.
Justice Brewer said, in most respects, Opai "appears to have been a model employee ... commended by her superiors".
However, the judge said, it also seemed her sense of responsibility caused friction with
other staff, which was a concern for the station's management.
She has also accused several senior police officers of being "members of an old boys' club", misleading the courts and engaging in retaliatory conduct.
"As the hearing of this case progressed I was increasingly saddened," Justice Brewer said in his decision.
"[Opai] had the respect and admiration of her superiors. Then Senior Sergeant Dexter Traill, her manager, was replaced on secondment by Senior Sergeant Culpan who did not know her.
"Ms Opai was shocked by his first draft of her annual appraisal."
She began to see malice behind any of Culpan's actions, Justice Brewer said.
"I fear Ms Opai is now obsessed with the way she perceives she was treated as an employee. This case is in point. There is no basis for a defamation case given the employment context, the nature of the statements complained about and the processes being followed when they were made."
Justice Brewer added the police were entitled to costs to be determined at a later date.
A police spokesperson told the Herald police acknowledged Justice Brewer's decision today but had no further comment.
Opai's lawyer told the Herald his client was disappointed with the result.
"She is grateful the court gave her the opportunity for her case to be heard (after two unsuccessful strike out applications by police), for she has genuine concern about the attempt to silence her in raising complaints about the misconduct of other staff," Woods said.
"She feels the judgment avoids addressing many of the concerns she raised, but she will continue to work towards bringing genuine change to address the current culture within the police. She is considering her legal options, including rights of appeal."
In the judgment, the judge also said he understood there was "a number of personal grievances against the police" currently before the Employment Relations Authority.
Earlier this month, the Court of Appeal ruled a former police officer cop was not constructively dismissed from the force after testifying against four cops accused of repeatedly bashing and pepper spraying a man in custody.
