Mr Bethune is charged with trespassing, vandalism, possession of a knife, obstructing business and assault, having illegally boarded the Shonan Maru 2 in Antarctic waters in February this year. He admitted to all but an assault charge in the opening session of the trial last week.
As is well known, Mr Bethune was in charge of the $3 million futuristic power boat Ady Gil - a boat which he had built and put his family's life savings into - when it was involved in a collision, in January, with Shonan Maru 2.
He and his crew, as part of the Sea Shepherd Conservation Society's anti-whaling efforts, had been harassing Japanese whaling ships in the Southern Ocean, attempting to disrupt and prevent their activities.
He continues to blame the captain of the larger vessel for a sudden change in course and a direct attempt to ram Ady Gil, such that a collision became unavoidable.
The exact sequence of events - who did what to whom - remains masked in confusion amid claim and counterclaim, the only certainty being there was a collision and, consequently, the unsalvageable Ady Gil later sank.
If this was a bitter end, as intimated in the Tokyo courtroom this week, to a dearly held dream, then its progress to that point had not been without other nightmares. Mr Bethune came into view with his vision to power a boat, the Earthrace, around the globe in record time using biofuels.
The first attempt in 2007 was hampered by mechanical hitches and tragedy when a Guatemalan fisherman was killed and another seriously injured following a collision off the coast of Central America.
Mr Bethune and the crew were detained for 11 days before being cleared of all charges. But the attempt had been derailed and a further voyage in 2008 was successful in setting the record.
Late in 2009, the Earthrace reappeared painted black and renamed Ady Gil under the auspices of the Sea Shepherd group.
Mr Bethune's subsequent collision, followed by his attempt to affect a "citizen's arrest" aboard the Japanese ship, garnered priceless worldwide publicity, drawing lasting attention to Japanese whaling activities.
Gaining attention is a skill the environmentalist and former oil company engineer has acquired and used to striking effect over the years.
It is hard to see the operation to remove his own body fat by liposuction in 2005 - to be converted into biofuel for Earthrace - as anything other than a publicity stunt.
And if he has proved single-minded in his various quests and adventures since, he has not always carried even his closest supporters with him - he and his wife separated in September last year. It might be argued the life of an activist is a thankless one, and requires a selfish focus.
But it might also be said there is a recklessness inherent in positioning a small but powerful and highly maneuverable speed boat in such proximity to a larger vessel that there is potential for collision; likewise, to board a vessel on the open seas, armed with a knife and expressing hostile intent, is the sort of action for which Somali pirates, or Israeli commandos, are roundly condemned.
Pete Bethune is doubtless sincere in his views on whaling - views shared by a many fellow New Zealanders - but what exactly did he expect? He is no stranger to drama on the high seas and whether he is hero or victim in the episode played out in the Tokyo court is a matter of opinion.
Publicity is part of his game. It is hard to know at this distance the extent to which his tearful supplication to the Japanese judiciary on Monday was for their benefit - or that of the world at large.
Many activists tread a fine line in their efforts to invoke sympathy for the cause, often teetering but a small mis-step from achieving precisely the opposite.
Nobody, least of all those who believe Japan's "scientific whaling" in the Southern Ocean to be bogus and unacceptable, would wish a prison sentence on this singular activist; but there might be those prepared to concede he appears, by his actions, to have asked for one.
