New Greenland hearing for anti-whaling activist Watson
The fourth hearing since Watson was arrested in July began at 9:00 am (1000 GMT) in Nuuk, capital of the Danish autonomous territory.
Watson's lawyer Julie Stage told AFP ahead of the hearing that she would ask for his immediate release, adding: "But unfortunately, realistically, that may not happen."
Stage said she was preparing an appeal to be filed with Denmark's Supreme Court over the Nuuk court's earlier ruling on October 2 to keep the 73-year-old in custody.
Watson was detained in Nuuk in July on a 2012 Japanese arrest warrant, which accuses him of causing damage to a whaling ship in the Antarctic in 2010 and injuring a whaler.
But Stage said she did not believe the criteria for his detention had been met.
Watson, who featured in the reality TV series "Whale Wars", founded Sea Shepherd and the Captain Paul Watson Foundation (CPWF) and is known for radical tactics including confrontations with whaling ships at sea.
He was arrested on July 21 when his ship, the John Paul DeJoria, docked to refuel in Nuuk on its way to "intercept" a new Japanese whaling factory vessel in the North Pacific, according to the CPWF.
'Inhumane treatment'
In a rare public comment on the case, Japan's Foreign Minister Takeshi Iwaya recently insisted the extradition request was "an issue of law enforcement at sea rather than a whaling issue".
Tokyo accuses Watson of injuring a Japanese crew member with a stink bomb intended to disrupt the whalers' activities, during a clash with the Shonan Maru 2 vessel on February 11, 2010.
Watson's lawyers insist he is innocent and say they have video footage proving the crew member was not on deck when the stink bomb was thrown. The Nuuk court has refused to view the video.
The custody hearings are solely about Watson's detention, with the extradition request being reviewed by Denmark's justice ministry.
In September, Watson's lawyers contacted the UN special rapporteur on environmental defenders, claiming that he could be "subjected to inhumane treatment" in Japanese prisons.
- 'Brave man' -
Watson had been living in France at the time of his arrest and has written to French President Emmanuel Macron to ask for political asylum.
World-respected British conservationist Jane Goodall told AFP last week she hoped France would accept his plea, calling him a "brave man".
As Watson's hearing got underway on Wednesday, several dozen supporters demonstrated outside city hall in Paris, chanting "Free Paul Watson" and holding signs reading "A hero doesn't belong in prison" and "Saving whales is not a crime".
French officials have previously urged Copenhagen not to extradite him, but have said offering asylum is complicated as a person must be in France to file a claim.
Japan, Norway and Iceland are the only three countries that still allow commercial whaling.