It's a highly unusual day in the High Court; Eminem's Lose Yourself plays to a room of unsmiling lawyers and a High Court Justice.

While rap isn't usually played in court, this song is the centre of a legal battle between the National Party, and those who own the copyright on the song.

A backing track used in a 2014 National Party campaign ad was alleged to be an unlicensed version of Eminem's song, and today the case is being heard at the High Court in Wellington.

Lawyer for the plaintiff Eight Mile Style, Gary Williams, said the National Party infringed copyright by using the song, or a substantial reproduction of it.


He said that even if the party only authorised the infringement, that in itself would be a breach of copyright.

Williams said it didn't matter if the song's lyrics weren't used.

He said there were three layers of copyright, covering lyrics, musical composition and then the sound recording itself.

"The song Lose Yourself, is without doubt the jewel in the crown of Eminem's musical work," Williams said, in his opening statements to the court.

"Not only did the song win an Academy Award for best original song in a movie, it also won two Grammy awards.

"In short, Lose Yourself is an extremely valuable song.

"The licensing of the song has been extremely carefully controlled. Despite many requests, it has only rarely been licensed for advertising purposes.

"When licensed, it can command in the millions of dollars. That's how valuable it is."


Williams said there was evidence that the track the National Party used had previously been named "Eminem ABBR", which they took as meaning "Eminem abbreviated".

He said that track name was later changed to "Eminem-esque".

He told the Court that when the ad was being put together, those working for the National Party were specifically looking for a track similar to Lose Yourself.

It had tested well with focus groups, who liked its "modern sound".

"[Eminem-esque] was found quickly because the track has 'Eminem' in the title," Williams said.

"So it was easy to find if you were looking for something that sounded like Lose Yourself."

The full track used in the National Party advertisement was also played in court.

The advertisement itself was then played.

Williams presented evidence to argue that National Party representatives knew copyright could be a problem.

An email chain included a quote from one National Party representative, questioning if their backing track was too similar to Lose Yourself.

"How can we be confident that Eminem doesn't think we're ripping him off?

"How do we ensure there is no liability with us?"

The email reply was that the National Party wasn't liable, because they were only buying a licence for a specific use of music.

The Party was told the composer would be liable for any copyright problems.

Williams was scathing after reading from the emails.

"That is just wrong, in law.

"Also, the focus is on not just whether it's an infringement. But whether they can shift liability to someone else."

Lawyer for the National Party, Greg Arthur, has given a brief statement to the court this afternoon.

He said the "clear position" of the National Party was to make sure there would be no possibility of copyright infringement.

He said this proposition can be proven in analysis of the songs.

"What makes Lose Yourself original is not mirrored in Eminem-Esque," said Arthur.

He also pointed out, that had the track been called anything that didn't reference the artist Eminem, it would have been lost in the multitude of other tracks in the Beatbox library.

"Copyright is not in any way proven by the name given to a piece of music," he said.

The court also heard evidence from the manager of Eight Mile Style, Joel Martin, who's flown to New Zealand from Detroit, Michigan.

He read a statement that outlines a timeline of events, beginning when the publisher first heard about the song the New Zealand National Party was using in its campaign ads in August 2014.

The case is set down for six days.