Detective Inspector Bryson Anderson, 45, was killed by Mitchell Barbieri, then 19, when a stand-off at Oakville escalated in December 2012.

Barbieri and his mother Fiona, who were mentally ill and convinced officers were corrupt, barricaded themselves inside after police were called when Mitchell fired a bow and arrow at his neighbours.

Insp Anderson was stabbed in the chest when police forced entry after unsuccessfully attempting to coax the pair out.

Deputy State Coroner Teresa O'Sullivan closed the inquest into the death on Tuesday, highlighting the results of a critical incident investigation.

"This case, and others, serve as a reminder of the enormously difficult job that police are required to do," she said in her written findings.

The faults with the operation included a lack of an adequate risk assessment, no clear understanding of who was in command and no clear beginning or ending to briefings.

But Ms O'Sullivan also noted that in the six years since the incident the police force has instituted major changes about risk assessment and siege responses.

Mitchell Barbieri pleaded guilty to murder and received a 35-year sentence, which was slashed to 21 with a minimum of 15 years on appeal.

His mother was sentenced to 10 years with a non-parole period of six for manslaughter.

Australian Associated Press