The spirited submissions were made Thursday at a sentencing hearing for Del Mastro, who was found guilty last fall of violating the Canada Elections Act during the 2008 campaign.
The Crown said it was essential that the former politician's punishment deliver a clear message.
"Nothing less than a period of imprisonment of nine to 12 months would adequately reflect the gravity of the offences and the degree of his responsibility," said prosecutor Tom Lemon.
"Moreover, anything less than real jail would fall short of properly denouncing his conduct and adequately deterring him and others from committing these or similar offences."
Lemon also asked that Del Mastro be required to pay $10,000 to the Peterborough Conservative Party Electoral District Association to reimburse money he "fraudulently obtained from them" for a contract with a data consulting firm.
Del Mastro— Prime Minister Stephen Harper's one-time point man on defending the Tories against allegations of electoral fraud — has maintained his innocence throughout his trial, and even called the judge's verdict her "opinion."
That adamant refusal to accept his convictions has made a sentence involving jail time all the more necessary, Lemon argued.
"Mr. Del Mastro does not seem to get the consequences of his actions and what he was convicted of, and the seriousness of those actions," Lemon said.
Del Mastro was consequently not a candidate for a rehabilitative sentence, Lemon said, and a discharge "is not even close to being on the radar."
The Crown's arguments were challenged by Del Mastro's lawyer, who repeatedly said time behind bars was far too heavy a penalty for his client.
"There is no prior judicial decision that says jail is the penalty that ought to be imposed for overspending under the Canada Elections Act," Del Mastro's lawyer Leo Adler said firmly. "It makes no difference how many different ways the Crown tries to say it, this is not a case of election fraud."
Adler contended that a discharge in the case was a possibility and said Del Mastro was not likely to commit such offences again as he was no longer an MP.
Del Mastro was found guilty of exceeding spending limits, failing to report a personal contribution of $21,000 to his own campaign and knowingly submitting a falsified document.
He faces a maximum penalty of one year in jail and a $2,000 fine on each of the three convictions.
His lawyer argued that if the Crown truly felt Del Mastro had committed electoral fraud, they ought to have charged him under the Criminal Code.
"To not do so while headlining breach of trust and fraud as the issues to be decided....is in itself arguably a fraud," Adler said. "It is not for the Crown to try to recast these three charges as corruption when they don't fall under that definition."
For the Crown, however, Del Mastro's offences appeared to have struck at the heart of the electoral system.
"The essence of the federal election financing system is to ensure that all Canadians have a fair and equitable chance to be heard and elected," Lemon said.
"These provisions seek to create a level playing field for those who wish to engage in electoral discourse. This in turn enables voters to be better informed. No one voice is louder than another."
By not fully declaring voter identification and get-out-the-vote calling services as election expenses, Del Mastro shifted the dynamics of the 2008 election campaign in his Peterborough riding, Lemon argued.
"Not claiming polling, voter ID and get-out-the-vote calling allowed Mr. Del Mastro to do more advertising. And in allowing him to do that, it allowed him to control more of the discourse during the election," he said.
Lemon also pointed out that Del Mastro was not a first-time candidate in 2008, and was familiar with campaign spending limits.
"The actions of Mr. Del Mastro were planned, deliberate and involved a high degree of sophistication," Lemon said. "These offences do strike a blow to democratic principles."
Del Mastro's sentencing hearing is set to continue April 28.
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