The family of Pc David Rathband has said the officer - who was blinded after being shot by Raoul Moat - was "let down by the people that could have prevented his death".
The comments were made as they attended the inquest into Pc Rathband's death, two years after he was found dead at his home.
The 43-year-old was left blind and fighting for his life after Moat shot him twice while he was on the run in July 2010.
Speaking outside 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 added: "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 do not accept this.
The findings of that investigation are contradictory to the evidence the coroner has 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.