US rapper Eminem is suing New Zealand's ruling political party over a music track it used for a campaign ad.
The star's Detroit-based music publishers claims the song was used in the 2014 advert by the National Party, was an unlicensed version of Lose Yourself, one of his biggest hits.
But the party's lawyers argue it was actually a track called Eminem-esque which they bought from a stock music library.
The two tracks were played in court on Monday when the copyright case began.
In 2014 when the case was filed, lawyer Steven Joyce said he thought the use of the song was "pretty legal," and that Eminem's team "are just having a crack and a bit of an eye for the main chance because it's an election campaign".
Spokesmen for both Joyce and the National Party said on Monday they would not be commenting while the case was before the court.
Garry Williams, the lawyer for Eminem's music publishers Eight Mile Style and Martin Affiliated, told the High Court in Wellington that the National Party had wanted a song that was edgy and modern but showed the party was dependable. He said the music fared better with focus groups than a classical piece.
He quoted from National Party emails, including one in which the song is described as an Eminem "sound-alike" and another in which an agent for the party wrote "I guess the question we're asking, if everyone thinks it's Eminem, and it's listed as Eminem Esque, how can we be confident that Eminem doesn't say we're ripping him off?"
Mr Williams said the emails showed it was "utterly clear" the party knew it was using a copyrighted song.
Outside court, Joel Martin, a spokesman for Eminem's music publishers, said he was surprised the two sides had not reached a settlement before the case began and that going to trial against an entity like a governing political party was unusual and extraordinary.
"The bottom line is we would never have permitted the use of the song in any political advertisement," he said.
He said the political views of the National Party were not a factor: "We are Americans and we don't know about politics in New Zealand," he said.
The judge-only trial is expected to last about six days.