The National Party spent $4800 on the music used in their 2014 campaign ad - music which as been labelled a "blatant rip-off" of Eminem's hit rap song Lose Yourself.
The campaign manager for the election that year, Jo de Joux, gave evidence in the High Court at Wellington this afternoon, saying the party sought "complete assurances" there was no risk of copyright infringement when using the track Eminem Esque in their campaign video.
When the clip was played to staff, one suggested the song sounded like Eminem's Lose Yourself, and de Joux was concerned about the association with the rapper as he had been associated with hate speech at the time, she told the court.
She also asked the production company that sourced the track for them to make sure it was safe for the party to use the music.
Marketing consultant Peter Moore, who was part of the production company set up for that year's election campaign, said he made a number of enquiries and was informed the party would not be at risk.
He was told if the party legally bought the music from a production library and it held an Apra Amcos licence, it would be fine.
He said he was "embarrassed" to be asking the different groups about the safety of using the track.
"[They] couldn't understand why I was asking about the appropriateness of using production music if they come from a recognised production library.
"I think they though I should have known this, with my experience in the industry."
De Joux said continued media comment on the song being similar to Lose Yourself was "unhelpful at a time when the party was trying to publicise its policies".
The party decided to change the music to keep the ad from distracting people from the campaign.
Yesterday music producer Jeff Bass gave evidence. He was the person who composed the original guitar riff for Lose Yourself.
He played the riff to the court on an acoustic guitar, before stating Eminem Esque was "a blatant rip-off" of the song, and was "like Lose Yourself Lite".
During the defence opening, lawyer Greg Arthur said the party paid $4802 for the licence for the track.
He said the song "no more than blandly referenced Lose Yourself."
"It's dangerous to be lured into listening to two pieces of music and thinking 'oh, that sounds a bit the same ... The copyright question is what is original in Lose Yourself and is there reproduction of a substantial part of that."
Arthur said he would call a witness who would say certain parts of Lose Yourself were unoriginal, so the copyright could not be infringed.
The trial will continue tomorrow.