The NSW Law Enforcement Conduct Commission has been investigating the circumstances surrounding the May 2023 incident, when a 46-year-old officer crashed a police-issued vehicle in a northern Sydney tunnel.
The off-duty detective left the damaged vehicle on a street and it wasn't until six months later he was charged with high-range drink driving.
The commission is due to hand down its report into the car crash and subsequent cover-up allegations on Thursday, with a recommendation it immediately be made public.
It would include several recommendations and findings, the watchdog said.
Internal police documents released to state parliament revealed the high-ranking officer, whose identity has been suppressed by a court, lodged an insurance claim saying the crash happened when he "fell asleep" at the wheel.
The detective had allegedly been drinking at a function before the crash.
He was subsequently accused of driving with a blood alcohol level of more than 0.15, an allegation the officer denies.
NSW Police Commissioner Karen Webb previously denied any cover-up, despite the force failing to issue public statements outlining the officer's charge.
She said disclosure had "slipped through the cracks" rather than being avoided deliberately.
Ms Webb denied the officer was "protected" during the six-month delay in charges being laid, saying it was not unusual for there to be a drawn-out investigation.
The officer is due back in court on September 27.
High-range drink-driving carries a maximum jail term of 18 months.
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