According to a police fact sheet, he had spent 12 unaccompanied minutes inside the perimeter after he walked around a boom gate and past a number of no-entry signs.

"It is mind-boggling that security at Australia's number one naval base was so slack," Mr Purgacz's barrister, Peter Lavac, told the Downing Centre Local Court on Tuesday.

Most of Australia's naval assets are in the Garden Island Fleet Base East or Perth's Fleet Base West. Handwritten notes seized in counter-terrorism raids in December 2014 allegedly referred to the base as a possible attack target.

Mr Lavac said his client was of excellent character and had recently spent three months off alcohol as part of a health regimen.

Mr Purgacz had been drinking with his mother and sister on December 23, starting with a bottle of rosé at Opera Bar before they shifted to the Golden Sheaf Hotel in Double Bay.