A military panel deciding whether a sailor sexually assaulted three colleagues while on tour of duty in Canada is hearing the trial judge's summing-up.

The 27-year-old man, who has interim name suppression, denies sexual violation by unlawful sexual connection and two charges of indecent assault.

He has been on trial at Devonport Naval Base in Auckland. Court martials can bring proceedings in cases of offences committed overseas.

Prosecutor Sam McMullan said the Navy able rate pursued two women in an apartment after a night out during a tour of duty in Victoria, British Columbia in August last year.

"Given the similarities between those two incidents, either they both happened, or [the defendant] has to be the victim of a remarkable coincidence for both of those two things to be false. Lightning doesn't strike twice," he said.

"The similarities, I suggest that you'll find in the evidence, that will help you determine that he did act in this particular way that morning, on the same night, the same place, he instigated both - although he says in relation to both they did. He went from one to the other, couch to the bed."

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Defence lawyer Paul Heaslip told the panel of five military members that having two allegations from different women about the same night was coincidental, and both women instigated the encounters.

"My learned friend says, 'what an unlucky man and lightning has struck twice', quite frankly, that's an overstatement. Apart from the fact that lightning does strike twice in some instances and you will all know that, the reality is that in this particular instance he's not saying he's unlucky.

"These are just coincidental, there is no correlation between these two things, and it is just a fact of life these things happened that night. They could happen on any two different nights, and you need to have care not to go 'ah, they're on that same night, therefore he's guilty".

The defendant denies that an indecent assault on a third woman in a taxi took place, also last August.

The prosecution says each complainant disclosed the sexual offending to a friend or colleague without knowing that the other two had also been assaulted.

The judge will sum up the case before the panel considers its verdicts