Krista Kach, 47, died following a 10-hour stand-off with police in Newcastle in September 2023 after a bean-bag round punctured her body and impacted her heart.
The Law Enforcement Conduct Commission (LECC), which monitors all NSW Police investigations into so-called critical incidents, requested to view the force's manual guiding the use of such "less lethal" measures.
Krista Kach died after being shot with a bean-bag round. (HANDOUT/KACH FAMILY)
The NSW Police Force on Wednesday was denied an appeal that would have stopped it being compelled to produce the document in its entirety.
Police argued the manual contained sensitive information not relevant to the watchdog's probe.
The "less lethal" manual addressed more than the use of the bean-bag rounds and dealt with police tactics and methodologies more generally, including those used by law-enforcement agencies overseas, the NSW Supreme Court heard previously.
Police also resisted an order to disclose personnel logs, which NSW Police counsel David Hume argued contained the names of operatives and could "lead to reprisals".
Mr Hume argued public-interest immunity should apply to parts of documents for which there was an overriding reason against disclosure.
But a panel of three judges rejected the police argument, deeming the legislated requirement for independent oversight and real-time monitoring by the commission took precedence.
Justice Julie Ward said it would make "a nonsense" of the watchdog's role if it was not provided with all the relevant material.
"The requirement for 'real time' monitoring of a critical incident investigation and the need for LECC to provide advice as to whether there has been full and proper investigation in compliance with relevant policies and practices mean that LECC must ... have access to all relevant documents," she said.
Justice Ward noted the parties could have been expected to reach a solution between themselves before bringing the matter to court, such as agreeing that only sections of the material relevant to the investigation were produced.
Instead, she said both sides appeared to have adopted a "blanket position".
The NSW attorney-general's barrister, James Emmett SC, argued the commission should be able to see everything investigating police could view.
One of the concerns held by police was that the commission could pass on the information to state parliament, allowing the material to make its way into a parliamentary report or similar public disclosure.
Mr Hume previously told the court the commission had been asked not to disclose the information to parliament and that request had been refused.
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