Earlier, Haggerty had also pleaded guilty to an assault in a family relationship and, in an incident unconnected to the blackmail, admitted exposing a young person to indecent material by posing on the internet as a 16-year-old boy to have explicit chats with a 14-year-old girl.
Judge Kevin Phillips said during the sentencing hearing in the Dunedin District Court that Haggerty had "really ruined the life" of the blackmail victim.
In her victim impact statement, the woman said she suffered every day, had trouble eating and sleeping, and was scared to leave her house by herself.
"Having to deal with this nearly pushed me over the edge … I've never been so scared of someone in my life," the woman said.
Haggerty appealed against his blackmail conviction and sentence to the High Court, on the grounds that the judge had erred in finding the ingredients of the charge proved.
However, Justice Cameron Mander dismissed the appeal and said the ingredients of blackmail had been proven.
Haggerty made a threat, tried to make the woman act in accordance with his will, and he intended to gain a benefit – in this case, continuing the relationship and regaining access to the woman's social media accounts.
Justice Mander's judgment included a partial transcript of an exchange of messages between Haggerty and his victim on June 20, 2020.
"Maybe I'll just post some screenshots of you on my page," Haggerty told her.
"Would you really be that low?" The woman asked.
"Yeah, 100 per cent," he replied.
Later that night, Haggerty sent an Instagram message to her objecting that she had blocked him and had called the police.
"Tell me y I shouldn't post those photos if that's how ur going to be towards me! Add me back on Snapchat ASAP please," Haggerty told the woman.
The district court was told that Haggerty had lost his "dream job" as an airport firefighter because of his convictions.
