An expert witness says it is not conclusive that Colin Matchim shook his infant daughter, causing brain damage.
Matchim has already been convicted of aggravated assault.
But the defence is trying to reopen the case to prove it wasn't a case of shaken baby syndrome.
Matchim was accused of shaking his infant daughter, August, in 2009. He was convicted in 2011 after a lengthy trial.
But sentencing was put on hold because his new lawyers wanted to put expert evidence before the court.
They believe the evidence will show that the injuries to August could have happened some other way.
On Tuesday, neuropathologist Dr. David Ramsay told the court that the injuries were consistent with shaken baby syndrome, but could have also been caused if August had had a pre-existing condition that interfered with the flow of blood in the brain.
Ramsay also noted that August didn't show any external signs of trauma, such as cuts or bruising.
Matchim had confessed to shaking his daughter, but recanted during the trial.
He said he believed that if he didn't confess, neither he nor his former partner would get custody of the baby.
Ramsay noted it's up to the police and courts to decide whether the confession was true or false.
The defence will put other witnesses on the stand to try to rebut the shaken baby syndrome theory.
The Crown will call witnesses to the contrary.