"We believe that the law is heavily on the side of Kim Dotcom and the others and we look forward to the court listening to the different arguments and making a ruling. We believe if we have a fair hearing and the court has the opportunity to hear all of the legal arguments and analyse them, they will rule in favour of Kim and the others."
The group was charged by the US Government in 2012 of conspiracy to operate websites used to illegally distribute copyrighted material via Dotcom's Megaupload website. They all maintain they are innocent.
If Dotcom does overturn December's District Court verdict and wipes out the decision to make him eligible for extradition to the US, it was expected the Crown would launch an appeal of its own.
If Dotcom fails, the lengthy legal scrap - and Dotcom's ability to remain in New Zealand - will probably still be years from reaching a conclusion, with the Court of Appeal and Supreme Court still options for Dotcom's defence.
"[If he loses] It will mean that he will have to go ahead and take his case to the New Zealand Court of Appeal and argue it there," Rothken said.
"Kim's a fighter. These issues are important not only for his well-being but society and the health of the internet and he's going to continue defending what is right here, what is just. Even if it means that he has to go to New Zealand's Supreme Court."
The defence case is expected to hinge heavily on whether an internet service provider can be held criminally responsible for the actions of its users.
"In addition, in New Zealand there is no criminal copyright infringement that would be applicable to the allegations in this case," Rothken said.
"This is a hearing that is not only important for Kim Dotcom but for all New Zealanders, and for that matter, everyone who has a stake in the internet globally."
Dotcom is also trying to have the court sessions streamed live on the internet.
The story dates back to 2012 and a raid on the Coatesville mansion Dotcom was living in at the time.
United States authorities had charged Dotcom and others with particular offences, including money laundering and criminal breach of copyright. Through New Zealand police, US authorities sought and obtained warrants to search for and seize material, including computers, relevant to the alleged offending.
Dotcom and his co-accused appealed the legality of the raid. In 2014 the Supreme Court ruled it was done legally.
In an eventful period since, Dotcom has revealed plans to relaunch his Megaupload file-sharing website in January next year - after the US Government took it down over piracy claims.
Despite hefty legal bills, Dotcom was still able to produce a music album in 2014's called Good Times. The album featured a song called Good Life - which Dotcom made a lavish music video for, the cost of which he estimated at $24 million.
Dotcom also had a fling with politics and founded the Internet Party which contested the 2014 general election in a failed alliance with the Mana Movement.
