I'm not a lawyer, but I understand 1st degree murder (except for some exceptions like the killing of police officer/prison guard on duty, forcible confinement/kidnapping/hijacking or sexual assault*) requires both proof of planning and deliberation. The scenario you describe sounds like an impulsive action driven by emotion (outrage).
Here's the section on planning and deliberation for first degree murder from WikiBooks Canadian Criminal/Law/Homicide:
Canadian Criminal Law/Offences/Homicide - Wikibooks, open books for an open world
"Planned and Deliberate[edit]
First degree murder must be "planned and deliberate".
[1]
There must be more than a "bare sufficiency of evidence" on planning and deliberation.
[2]
A "planned" murder refers to one that is "conceived and carefully thought out prior to being committed".
[3]
It must have "a design or scheme be arranged beforehand."
[4]
However, it can be "simple and need not necessarily be in place for a long period of time"
[5]
A "deliberate" murder is not impulsive. It must be a considered act
[6] where "he thinks about the consequences and carefully thinks out the act, rather than proceeding hastily, rashly or impulsively"
[7]
The elements of "planned and deliberate" can be proven on by circumstantial evidence.
[8] However, it cannot be equivocal or speculative of whether it was "planned and deliberate".
[9]"
* other exceptions are criminal harassment, contract murder, terrorist activity, criminal organization and intimidation
I'm assuming the crown will present some evidence showing planning and deliberation, we just haven't heard it yet.
As well, DM's cell phone "pings" are going to be used (as they were in the 2 previous trials), they agreed on cell phone tower evidence today. The "pings" will probably show that he went to Maplegate that night and then returned back to MS' place in Oakville.