Dotcom's epic extradition battle has dragged on for more than six years, starting in January 2012 when armed police acting on an FBI request raided his Auckland mansion.

The 44-year-old German national is accused of industrial-scale online piracy via his Megaupload empire, which US authorities shut down when the raid took place.

If sent to the United States he will face charges of racketeering, fraud and money laundering carrying jail terms of up to 20 years.

Dotcom and his three co-accused -- Finn Batato, Mathias Ortmann, Bram van der Kolk -- maintain their innocence and will challenge the legitimacy of their arrests this week at the Court of Appeal in Wellington.

If the appeals court rules Dotcom is eligible for extradition, a process that could take months, he will have limited options for overturning the decision.

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