The National Party has returned for an encore in its battle with Eminem over the use of the rapper's music in an election advertisement.
Tuesday's appeal hearing comes after the High Court in October ordered the party and its national President Greg Hamilton to pay $600,000 in damages for using a piece of music called 'Eminem Esque' in a 2014 ad.
A trial in May 2017 found the "soundalike" music which National had licensed for $4802 had substantially copied 'Lose Yourself' - one of Eminem's biggest hits and the winner of both Grammy and Oscar awards.
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The copyright for the song is administered by two American companies - Eight Mile Style and Martin Affiliated - which initiated the court action and have now cross appealed asking for damages to be increased.
During the High Court trial last year, the two companies had accused the National Party of intentionally trying to avoid paying for using the song by seeking production music that sounded similar like 'Lose Yourself'.
In response, National argued the companies responsible for producing, distributing and licensing 'Eminem Esque' should be liable for any damages because the party sourced the music in good faith.
National's lawyer Greg Arthur has reprised that position in the Court of Appeal in Wellington, adding that he believed High Court Justice Helen Cull focused too much on Eight Mile Style in her decision, labelling her approach "licensor-centric".
Mr Arthur told the Court of Appeal the $600,000 damages figure - seen as a kind of "hypothetical license fee" for Lose Yourself - was too high as it didn't take into account the fact any license would only be for New Zealand where the television advertisement was screened.
Tuesday's decision is expected to be reserved, meaning the outcome of the appeal might not be known for several weeks or months.
The original two-week trial in May 2017 was a musical affair that included courtroom scenes of lawyers listening to 'Lose Yourself' on repeat and a live acoustic performance of the song's distinctive guitar riff by co-writer Jeff Bass, a Detroit-based producer who flew to New Zealand to give evidence.
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Mr Bass told the court he and the other composers of the track had turned down huge offers to license the song for political purposes, and they would never had allowed National to use it regardless of the money on offer.