A discredited former engineer who declared an Ontario mall structurally sound just weeks before its deadly collapse five years ago was acquitted of criminal negligence on Thursday.

While critical of how Robert Wood conducted himself, Superior Court Justice Edward Gareau in Sault. Ste. Marie, Ont., nevertheless found insufficient evidence to convict him.

Teresa Perizzolo, daughter of one of the two women who died in the mall collapse, said she was disappointed, but said Gareau had done his best.

"I was hoping somebody would get nailed with it," Perizzolo said in an interview. "But the law's the law, right, so it's pretty much done the proper way I guess."

On June 23, 2012, part of the rooftop parking garage at the Algo Centre Mall in Elliot Lake, Ont., crashed into the shopping area below.

Evidence was that a key steel support had rusted due to years of leaking and salt-water penetration. The leaking was so pervasive, some members of the community dubbed the centre the "Algo Falls."

Wood had pleaded not guilty to two counts of criminal negligence causing the deaths of Lucie Aylwin, 37, and Doloris Perizzolo, 74, who died in the rubble. He had also pleaded not guilty to a third count of criminal negligence causing bodily harm to 80-year-old Jean-Marie Marceau, who was badly hurt.

Faced with the unstable building, emergency crews spent days frantically trying to reach the victims before officially calling off the search, much to the consternation of the community.

Wood, who is now in his mid-60s and retired, inspected the building in 2009 and again in 2012 in the weeks before the collapse.

In May 2012, he told the mall's owner that steel supports at the shopping centre showed surface rusting, but were otherwise "structurally sound." He testified both at a far-reaching judicial inquiry and during his trial that he saw nothing to indicate that any imminent danger existed.

However, he did admit to having changed his final inspection report by, among other things, deleting photographs of a corroded steel beam and yellow tarps strung to collect water leaking into a mall store.

Wood, who had been stripped of his professional engineering licence in November 2011 for misconduct unrelated to the mall, did not mention the changes to his partner, who had signed off on the inspection report.

Wood did not comment after Gareau spent four hours explaining how he had arrived at an acquittal. However, his lawyer Robert MacRae said the verdict was "certainly bittersweet."

"It's still a very terrible tragedy," MacRae said.

Given the acquittal, MacRae said a constitutional challenge based on the lengthy delay between charges being laid and the trial was now deemed abandoned. A hearing had been set for July.

Gareau had reserved his decision in February after about four months of hearings.

Police charged Wood criminally in January 2014. It was not immediately clear what would now happen to charges laid earlier under provincial worker-safety rules that were put on hold pending disposition of the criminal case.