An Alberta mother who admitted to drowning her two young sons in a bathtub was found guilty of manslaughter Friday, and not the more serious charge of murder, in a case that shocked the country.

Allyson McConnell had been charged with two counts of second-degree murder in a case that focused on her state of mind at the time of the killings in 2010.

But Justice Michelle Crighton said there wasn't enough evidence to prove McConnell had intended to kill the two boys.

She said there was a "black hole" in the prosecution's case that left her with little information to reach a guilty verdict on the murder charges.

"The accused is entitled to the benefit of that doubt, and accordingly, she cannot be convicted of second-degree murder," Justice Crighton told the court.

There were no witnesses and McConnell had testified she couldn't remember anything the day the two died.

The two children – 10-month-old Jayden and two-year-old Connor - were found dead in a tub of freezing cold water by their father, Curtis McConnell, on Feb. 1, 2010 in their Millet, Alta. family home.

Curtis McConnell and his family were in the courtroom for the verdict and he was visibly upset when it was read, CTV Edmonton's Bill Fortier reported Friday.

Allyson McConnell, sat emotionless in the prisoner's box as she had throughout much of the trial, he told CTV's News Channel in a telephone interview.

"I think that the crown proved murder so I am disappointed in that regard," Crown prosecutor Gordon Hatch told reporters outside the courthouse. "But a verdict of murder would not have been anymore satisfying in the sense that these boys are dead and we can't do anything about that."

Hatch said he would take time to study the judge's ruling before deciding how to proceed.

The two sides painted different pictures of Allyson McConnell during the trial.

The prosecution said she killed the boys out of revenge against her husband because of a bitter divorce that included a custody battle.

The defence suggested Allyson McConnell was too strung out on alcohol, sleeping pills and suffering from depression to form the intent required for a conviction.

It's not known when exactly during a three-day span at the end of January that McConnell drowned the boys, court heard.

But on the morning of Feb. 1, McConnell drove to Edmonton, parked at a toy store, had lunch and then attempted suicide by jumping off a bridge onto a busy highway.

McConnell, who is originally from Australia, had a long history of suicide attempts that began after she was impregnated by her father at 15, court heard during the trial.

Police found several searches on her computer relating to suicide and drowning, including one that asked: "How long does it take to drown?" and another asking: "How long does it take to die from strangulation?"

Officers also found a rope tied to a joist in the basement with a chair underneath it.

Court also heard Curtis McConnell frantically ran to a neighbour's house after finding the boys dead to get someone to confirm that what he was seeing was real and not his imagination.

His wife had left her wedding ring on the toilet seat.

The couple's divorce had been bitter and they had fought over custody of the boys, whom McConnell wanted to take back to Australia with her, court was told.

Curtis McConnell has also filed a lawsuit against his wife seeking damages for the children's deaths.

Sentencing is scheduled for May 9.