Lawyers for Toronto Police Const. James Forcillo argue the officer should get a suspended sentence.
That's only if they lose their legal fight to overturn Forcillo's guilty finding on attempted murder charges.
The police officer at the centre of the 2013 streetcar shooting death of Sammy Yatim is making his appeal at a downtown Toronto courthouse.
In July 2016, Forcillo was sentenced to 6 years in prison for firing a second volley of gunfire at Yatim, while the teen lay bleeding to death on the floor of a TTC streetcar.
Forcillo's legal team calls the penalty "grossly disproportionate."
It argues that Canada's mandatory minimum penalties for gun crime cannot apply in the officer's case because the officer was required by law to carry a firearm in the commission of his duty as a cop.
Forcillo's lawyer contends the court cannot declare a police officer as morally culpable as a criminal who picks up a gun in order to cause chaos.
The trial judge who sentenced Forcillo called the constable's actions "an egregious breach of the public's trust" and delivered a prison sentence one year over the mandatory legal minimum.
Superior Justice Ed Then said that the move was intended to put other police officers on notice.
Also at issue is the prosecution's decision to separate Forcillo's two volleys of gunfire into two separate events, and two separate charges.
Appellant counsel Michael Lacy told a 3-judge Appeals panel on Monday that there is "no air of reality'' that those two bursts of gunfire were separate events.
During the trial, the jury heard hours worth of evidence, including testimony from Forcillo himself, concerning why he decided to open fire a second time.
The Crown will argue that it was "logical" and "not unreasonable" to split Forcillo's actions into two separate charges and that it is "not inconsistent" with the law.
Forcillo was the first officer who responded to a 911 call about someone brandishing a knife on a Dundas St. streetcar.
He claimed during the trial that he opened fire in self-defence, to stop an "imminent attack" by Yatim.
Forcillo has been suspended without pay by Toronto Police since he was handed his sentence.
The appeal hearing resumes on Tuesday morning.