Detective Sergeant Eve Doherty's lawyers told the jury at her trial that she was a whistleblower motivated by a wish to expose corruption and mismanagement at the highest levels of the State.
Even her own barrister accepted that the vile accusations she was levelling at Liz Howlin, a solicitor working in the Directing Division of the DPP, were untrue.
But he said they could still be genuinely held.
The prosecution suggested a much simpler motive. They said that Doherty was motivated by irrational, jealous dislike of her boyfriend's ex-wife - to the point that she became obsessed with Ms Howlin and could no longer control her jealousy.
Yesterday the detective garda was found guilty of harassing the State solicitor by sending her abusive letters and emails.
The first poison pen letter sent by Doherty to Ms Howlin provides the best evidence for the detective being motivated by a personal gripe. This letter, hand-delivered to Ms Howlin's home in Blackrock, Dublin, called her a "pompous arrogant c***, a hag and a midget". Making references to her son, it commiserated with him for "having a c*** of a mother like you".
But crucially Doherty referred to Ms Howlin's ex-husband, who had separated from her some years earlier, and suggested that it hadn't taken him long to decide to leave her.
This was the beginning of a hateful campaign that would see Doherty going to greater and greater lengths to get at Ms Howlin.
Two months later, Doherty wrote a letter to Ms Howlin's boss, the DPP Claire Loftus. This was the first time she introduced the name of Wexford TD Brendan Howlin into her campaign. She wrongly claimed the TD was the uncle of Ms Howlin. They are in fact distant cousins. Doherty went on to tell Ms Loftus that her employee was using every opportunity to destroy her good name and had used political connections to try to stop her recent appointment to the top job.
Doherty warned Ms Loftus that Ms Howlin was "the most two-faced, hard-faced b****".
Of course, the letter was seen by Ms Howlin and unsurprisingly caused her great distress.
But things escalated. Just weeks later, a neighbour of Ms Howlin called to her door to show her a leaflet.
The garish, printed leaflet had a photograph of Ms Howlin alongside her job title and her address and house number. It had wild accusations about Ms Howlin using political influence to protect a family of "drug dealers" from prosecution.
Doherty even named the family - a respectable family whose son was caught with a small quantity of cannabis. With no previous convictions, the son's case was struck out.
The prosecution told the jury these were not the efforts of a whistleblower to expose political cronyism.
Doherty next decided she needed to reach a much bigger audience.
She began setting up anonymous email accounts on Hushmail, a service that promises enhanced email security including encryption. Over the next year, she would use these email accounts to send emails to 779 recipients. These included newsrooms, universities, the Courts Service and the Financial Ombudsman.
One of the first emails, sent in February 2012, made wild allegations about then-justice minister Alan Shatter. It also gave out his private address and that of the DPP.
The emails repeated false and defamatory claims that Mr Howlin would ring "his sister" in the DPP so that she would "pull" files to ensure there were no prosecutions of anyone connected to Mr Howlin or the government.
By September 2013, Doherty had taken to disguising herself in a wig and sunglasses to go into the city centre internet café to send more emails.
She even sent herself abusive letters in order to make it look like somebody else was writing to her, the prosecution said.
Her sentence hearing takes place in October.
A garda has gone on trial accused of harassing a State solicitor by describing her as politically corrupt in a series of "hideous" and "vitriolic" letters and emails.