The family of PC David Rathband have said he was "let down by the people that could have prevented his death" as they attended his inquest, two years after he was found dead at his home in Northumberland.
The 43-year-old was left blind and fighting for his life after gunman Raoul Moat shot him twice while he was on the run in July 2010.
Speaking on the steps of Moot Hall, Newcastle, Mr Rathband's father Keith said: "The evidence that the coroner has been given identifies that David was let down by the people that could have prevented his death.
"The findings of the coroner may be a foregone conclusion to many. Our hope is he finds David's death was preventable in the circumstances."
Mr Rathband's sisters, Debbie Essery and Julie Reece, joined their father in expressing concerns about previous events.
Ms Essery said: "Northumbria Police investigated a complaint made by David's brother Darren.
"Into those issues the investigation found there was no case to be answered.
"As a family, we don't accept this. The findings of that investigation are contradictory to the evidence the coroner's been given."
PC Rathband won national praise for his battle against disability and for setting up a charity to help other emergency workers injured in the line of their work.
He was found hanged at his home in Blyth, Northumberland, on February 29, 2012.
Mr Rathband, a father of two, was estranged from his wife Kath, and reportedly told her she would "look nice in black" when they spoke on the phone for the last time.
His twin Darren, a police officer in Australia, is not attending the inquest, and his widow Kath and son Ash walked in separately from the dead officer's father and sisters.
Before blasting the unarmed traffic officer, Moat shot and injured his ex-girlfriend Samantha Stobbart, and killed her boyfriend, 29-year-old Chris Brown.
Moat shot himself in Rothbury, Northumberland, during a standoff with police at the end of a week-long manhunt.
An inquest into Mr Brown's death concluded last month he was unlawfully killed.