A new trial started Monday for an Edmonton foster mother previously convicted of manslaughter.  

Lily Choy, 36, is charged with second-degree murder in the January 2007 death of a three-year-old boy, who cannot be named under Alberta's Child, Youth and Family Enhancement Act.

A jury found Choy guilty of manslaughter in November 2008 and she was later sentenced to three years in prison.

In March 2010, the Alberta Court of Appeal ordered a new trial after finding the judge in the first trial gave the jury a "legally incorrect exhortation" to reach a verdict after they said they were deadlocked.

Choy's second trial is now underway before judge alone in Edmonton's Court of Queen's Bench.

Evidence heard Monday included the recording of a call Choy made to 911 about an injured three-year-old boy who had collapsed on the floor for no apparent reason.

"His eyes are open, and he's making deep breaths occasionally but we can't get him to react to stimuli," she tells the operator.

In the tape, Choy says the boy had been harming himself recently. But the prosecutor told the court the death was not accidental and the injury could not have been self-inflicted.  The cause of the boy's injury will be a key issue in the case.