An Ottawa judge is set to decide next month whether an on-ice collision during a 2012 hockey game was an incidental hit or an aggravated assault. 

Gordon MacIsaac was convicted of aggravated assault after the initial trial in 2013, but a new trial was ordered after the Ontario Court of Appeal found the judge relied on her knowledge of "hockey strategy" rather than expert testimony.

During the last 47 seconds of a March 2012 game of the non-contact Ottawa Senior Men's Hockey League, MacIsaac and Drew Casterton collided.

Casterton was knocked unconscious, broke two teeth and suffered cuts on his face. 

Initial trial marred by 'speculative reasoning'

In the appeal's decision, a panel of three judges found Justice Diane Lahaie erred by "engaging in speculative reasoning."

In her decision, Lahaie wrote the actions described by defence witnesses "defied logic" because of their hockey positions and locations on the ice. 

Lahaie sided with the evidence presented by a referee, stating the players who testified showed a "clear bias" depending on which team they played for.

Defence lawyer Patrick McCann said the February retrial included testimony from the same witnesses. 

The decision in the retrial is set to be handed down April 18.