"It doesn't change much for me. His findings realistically don't give any answers to what actually happened. I just don't understand what happened. There is no closure."
Mr Fitzgerald said he did not understand why there had been no trace of his wife, despite extensive searches of the lake.
"You see other missing people in water, even salt water and they are found. It's hard to deal with not knowing."
He said he never hid the truth from his son, telling him from the start that his mother was dead.
"He has a reasonable understanding ... he has accepted it is full and final. He still has memories and Kelly's photos are everywhere. He is old enough to remember her. He's a good kid with a loving nature."
The family home was full of memories of Kelly, Mr Fitzgerald said.
"Her clothes still hang in the wardrobe and are folded in her drawers. Everything has been much the same - it's been hard to deal with."
Trying to cope with the loss of his wife, becoming a solo parent and running a business took its toll on Mr Fitzgerald earlier this year following a lengthy battle with Work and Income for financial help.
"I'm still very bitter about what went on. The whole business was incredibly stressful. It scarred me."
In his findings into Mrs Fitzgerald's death, Dr Bain said it was a common misconception that there needed to be a waiting period of seven years before a missing person could be legally declared dead.
He noted Mrs Fitzgerald had suffered post natal depression and had previously tried to take her own life.
On August 10, 2009, she dropped her son off and went to work for about 45 minutes before telling her boss "I'm not up to it, I just need to go home".
Late that night her car was found abandoned beside the lake with her keys, wallet and the clothes she was wearing that morning inside.
In the days following her disappearance the lake and surrounding area were thoroughly searched by the Police Dive Squad and Search and Rescue but her body was not found.
Dr Bain said a note had been found at the Fitzgerald home from her saying: "goodbye and sorry".