An Alberta man says he's relieved to be home with his young son after spending four years in an Australian prison before being acquitted in the killing of his ex-wife.

Rory Christie, who was arrested in 2001 and found guilty of murder in a 2003 trial, was acquitted at a second trial Friday. His initial conviction was overturned in March 2005.

Christie has finally been reunited with his nine-year-old son Fraser, who has been living with Christie's parents in Lloydminster, Alta.

"It's great to be back here with my family," he told CBC News.

"There's some pretty dark times when you've got a young son. He's spending Christmases without you. All the little things, like when they hurt themselves, get colds and stuff, and you can't be there for them. It makes for some pretty tough days."

Susan Christie was last seen alive in her Perth apartment in November 2001. No body has ever been found.

The couple had been separated for a number of years and Rory Christie had custody of their son.

"She had fallen ill, alcoholism, she tumbled down that path," he said. "And subsequently she'd gone missing. They charged me with her disappearance."

His lawyers had lined up an Edmonton blood expert to state that the evidence introduced in the first trial – that large amounts of Susan Christie's blood were found on one of his ties – was analyzed using out-dated technology.

According to Australian news reports, Joe Slemko's report estimated that just 70 millilitres of blood were found in Susan Christie's apartment, and that 2,000 ml would have to be lost before someone died.

He didn't testify because a judge threw out the case after hearing other evidence. Rory Christie had also said that the blood found on his tie – which his expert said amounted to a small drop – was from a nosebleed his wife suffered.

The blood evidence the prosecutors used was "proven completely false," said Christie, who has always maintained his innocence.

"We found a lot of evidence that was hidden from us before," Christie alleged, adding that it included audio surveillance tapes the defence hadn't been made aware of. "A lot of evidence was lost."

Australia's director of public prosecutions has said Christie's case won't be appealed.

"It's finally done," Christie said.

But he realizes getting his life back to normal will take time.

"Now I've got to try to start over again," the computer expert said. "Fortunately, I've got a great family, they really loved me and supported me."