A Royal New Zealand Navy sailor has apologised for the shame he caused after drinking 24 beers and allegedly breaking into a US Navy house while stationed at Pearl Harbour.

Combat systems specialist Mitchell Jason Campbell, 23, allegedly took a wallet, compass and sharpening stone belonging to the 15-year-old son of a US naval officer during the July 1 break-in.

He has denied three charges of burglary, theft and wilful damage, and is on trial by court martial at the Devonport Naval Base in Auckland.

Campbell's watch supervisor Rick Smith said he was "hardworking, honest and loyal".

"He's a quiet chap by nature. He's a good man. His integrity is second to none."

This morning, Campbell said he could recall having 24 beers and a rum and Coke. He said he could not remember anything between leaving a club where he had been drinking with colleagues and waking up in a backyard with blood on his T-shirt.

He said he felt "terrified" when he was told about the house's broken window, his ID being there and the stolen items.

"It didn't make sense to me. It's not in my nature to do anything like that. I'm sorry for the disgrace I have caused."

Campbell told the court he had been in the Navy since 2012 and loved his job. He denied claims by the prosecution he was an "incompetent burglar".

"I am not a burglar, I would never in my right mind steal stuff that did not belong to me."

He admitted finding a wallet and other items not belonging to him when he returned to the pier and putting them in his locker.

However, he said he was still drunk, had to get ready for work and hadn't thought much of them.

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Yesterday, two of Campbell's colleagues, who had been with him on the night, told the court they didn't remember him being grossly intoxicated. If he had been, he would have been escorted back to the ship.

The court was told Campbell allegedly climbed 5m to the second storey of a US naval officer's house in the early hours of the morning after drinking with colleagues at a garden bar and club, and purchasing food from Taco Bell.

He allegedly broke into the house by smashing the bedroom window of the officer's 15-year-old son, who was sleeping in a different room at the time.

Panicked and with a cut hand and forearm, Campbell dropped his wallet, which included his Navy ID and a Taco Bell receipt, prosecutor Captain Robert Goguel said. He also left a bloodied packet of cigarettes and a lighter in the room.

He then went to the upstairs bathroom, the office - where he dropped his Chicago Bulls hat - and to the kitchen where he allegedly stole the officer's son's wallet, compass and sharpening stone.

Finally, he went to the downstairs bathroom where he left a bloody towel and T-shirt, Goguel said.

DNA testing of the blood revealed it was 600,000 million times more likely to come from Campbell than any other person, the court was told.

Campbell was with the HMNZS Te Kaha at Rim of the Pacific international maritime exercise. He was on shore leave on the night of the break-in.

Campbell later returned to the pier and was denied entry as he didn't have his ID.

A medic escorted him on board and helped with his injuries. He gave no explanation for his lack of ID or injuries.

The US officer, who cannot be named to protect the identity of his son, reported the break-in to the Naval Crime Investigative Service at Pearl Harbour.

A court martial is presided over by a judge, and its findings decided upon by a bench of military members independently selected from qualified officers. The trial is expected to finish mid-week.