In a rare move, the Alberta Court of Appeal overturned an Edmonton jury's "unreasonable" verdict Monday, replacing the murder conviction of Katrina Effert with a lesser one of infanticide.

Katrina Effert in a photo from 2008 outside of the Wetaskiwin courthouse. CBCEffert was 19 years old on April 13, 2005 when she secretly gave birth in her parents' Wetaskiwin, Alta. home, strangled the baby boy with her underwear and threw the body over a fence into a neighbour's yard.

A Wetaskiwin jury found Effert guilty of second-degree murder in 2006, but the verdict was overturned by the court of appeal. A second jury trial was held in Edmonton in 2009, ending with the same verdict.

The court of appeal based Monday's decision on the testimony of two clinical experts during the second trial, both who testified Effert's mind was disturbed at the time of the killing.

While both had limited experience with infanticide cases, their evidence was not contradicted during the trial and should have been given more weight by the jury, the appeal court ruling said.

Verdicts must be protected

In its written decision Monday, the court acknowledged jury verdicts should not be overturned lightly.

There are however cases where the verdict of the jury cannot be sustained,'—Alberta Court of Appeal

"Juries are an important part of the criminal justice system and the integrity of their verdicts must be protected," the court said.

"There are however cases where the verdict of the jury cannot be sustained," it said.

"Where a verdict is unreasonable, in the sense that it cannot be supported by the evidence before the jury, then the jury must have made an error in its analysis or failed to understand the instructions given."

It's not possible to know the jury's reasoning in their deliberation, the ruling said.

"Perhaps this jury was distracted by the tragic circumstance of the death of a newborn infant."

Prosecution overzealous: judge

In fact one judge pointed to the "overzealous" and "unrestrained" tenor of the prosecution.

For example, the prosecution displayed 58 graphic, colour autopsy photos even though the cause of death was not an issue as Effert had already admitted to strangling the infant, said Justice Peter Martin.

"This conduct, he said, "could only have made the jury's already difficult task — to decide the case fairly and dispassionately — more difficult."

Alberta Justice rejected the criticism.

"We reviewed the exact remarks that were made in court, the context in which they were made, and the relevant evidence at the time, and we do not share the judge's concerns," said spokesperson Carla Kolke.

Alberta Justice is now considering appealing the ruling to the Supreme Court of Canada, said Kolke.

Effert's lawyer, Peter Royal, declined an interview Monday, but said he would not be surprised if Alberta joined another appeal of a similar case from Ontario before the Supreme Court of Canada.

Effert was facing a life sentence without parole eligibility for 10 years on the more serious charge.

Infanticide carries a maximum sentence of five years.

Effert will be sentenced on the infanticide charge on June 17.