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HOW IS CONFLICTING EXPERT EVIDENCE TO BE CONSIDERED BY A TRIAL JUDGE

In R. v. K.J., 2021 ONCA 570, August 19, 2021, the accused was convicted of the offence of aggravated assault in relation to her thirteen-month old son (NT).  At the trial, there was conflicting expert evidence as regards the injuries to the child.  The Ontario Court of Appeal summarized this evidence in the following manner (at paragraphs 13 and 14):

The Crown’s expert, Dr. Baird, opined that no underlying medical condition or recent illness could explain N.T.’s injuries and concluded that the only “remaining plausible explanation” was “severe inflicted head trauma,” which he believed had to have occurred on the change table when the appellant was changing N.T.’s diaper. He testified that while persons with injured brains can have seizures days after an accident, the type and degree of retinal hemorrhages N.T. suffered were not consistent with the minor short falls and other incidents described by N.T.’s parents and the appellant. He believed that if N.T.’s injuries had been caused by an accident, the accident needed to be so significant and dramatic that the event would not have gone unnoticed by his caregiver. He was of the view that since N.T. exhibited normal neurological function before July 20 and “because there was no report of any episode of accidental trauma which has any authoritative accepted scientific literature to be associated with the types of hemorrhages that he has”, N.T.’s brain injury was caused by severe acceleration/deceleration forces that were inflicted upon him immediately before the hospital visit.

The appellant’s expert, Dr. Ramsay, also ruled out any underlying disorder or disease as a possible cause for N.T.’s subdural bleeding. He agreed that N.T.’s subdural bleeding, retinal hemorrhages, and damage to the brain (“the triad”) are typical of acceleration/deceleration injuries. However, he cautioned against reliance on the triad alone because of its unreliability in demonstrating an impact head injury. He noted that there were factors present which went against the finding of an acceleration/deceleration injury, including N.T.’s large subdural hemorrhage, and the localized brain damage that was explained by an expanding haematoma. In addition, he testified that N.T.’s injuries, specifically his retinal hemorrhages and subdural hemorrhages, can be caused by short falls. Dr. Ramsay explained that adults and children can suffer from subdural haematomas without being symptomatic immediately. They experience a “lucid interval” of seeming wellness until the accumulation of subdural blood and consequent compression of the brain results in drowsiness, headache, and loss of consciousness. Dr. Ramsay opined that while N.T.’s injuries could have been caused by the application of acceleration/deceleration forces, they also could have been caused by one or a combination of the three short falls he suffered.

The Appeal:

The accused appealed from conviction. The Court of Appeal indicated that the appeal turned “on the trial judge’s treatment of the medical expert evidence on the causation of N.T.’s head injury” (at paragraph 3).

The Court of Appeal:

A new trial was ordered.

The Court of Appeal suggested that “[i]n the case of conflicting expert evidence that is crucial to understanding the material issues to be decided, it is tempting for a trier of fact merely to choose one expert over another, and to allow an expert witness’s evidence to distort the fact-finding process and overtake the task of objectively assessing the totality of the evidence at trial…It is common ground that such an approach constitutes legal error” (at paragraph 18).

The Court of Appeal held that “the trial judge’s approach to assessing the expert evidence on causation was flawed. She first chose which expert she preferred and then viewed the other expert’s evidence and the rest of the trial evidence through that lens. This was an error. The trial judge should have considered the expert evidence, along with all the other evidence at trial, through the analytical framework prescribed by the Supreme Court in R. v. W.(D.),[1991] 1 S.C.R. 742, to determine whether the Crown had met its heavy burden of proving the appellant’s guilt beyond a reasonable doubt” (at paragraph 17).

The Court of Appeal concluded that “the trial judge’s reasons demonstrate that she did not consider the expert evidence in relation to the totality of the evidence at trial. Instead, she determined in isolation that she preferred Dr. Baird’s evidence before she turned to the rest of the trial evidence, which she then assessed through the fixed lens of Dr. Baird’s opinion. This led her to misapply the W.(D.) framework. She rejected not only the defence expert evidence of Dr. Ramsay, but all the defence evidence because of its inconsistencies with Dr. Baird’s opinion. Further, she never meaningfully considered whether Dr. Ramsay’s evidence, along with all the other evidence that supported the defence, left her with a reasonable doubt as to the appellant’s guilt” (at paragraph 22).

Finally, the Court of Appeal indicted that “[b]y preferring one expert over another, without examining the expert evidence through the W.(D.) framework and in the context of the totality of the evidence, the trial judge fell into legal error. The expert evidence was crucial to the principal issue of the causation of N.T.’s head injury. A new trial is therefore required” (at paragraph 30).