We must reserve the blunt tool of the criminal justice system for the most serious cases. The criminal justice system can’t do everything. It is not a panacea for all of society’s ills.
Justice Michael Moldaver, speaking at the National Criminal Law Program in Ottawa on July 8, 2019
The Supreme Court of Canada has affirmed repeatedly that prosecutorial discretion is an essential attribute of the justice system. Indeed, the exercise of prosecutorial discretion is critical for curtailing the unnecessary and unproductive use of an increasingly complex and costly criminal trial process when other just solutions may be more appropriate.
The underlying importance and purpose of prosecutorial discretion is perhaps best understood by examining the following passages from the Supreme Court of Canada:
The existence of the discretion conferred by the statutory provisions does not… offend principles of fundamental justice. Discretion is an essential feature of the criminal justice system. A system that attempted to eliminate discretion would be unworkably complex and rigid. Police necessarily exercise discretion in deciding when to lay charges, to arrest and to conduct incidental searches, as prosecutors do in deciding whether or not to withdraw a charge, enter a stay, consent to an adjournment, proceed by way of indictment or summary conviction, launch an appeal and so on.
R. v. Beare,  2 S.C.R. 387 at para. 51
…Parliament's enactment of dual procedure offences recognizes that certain crimes can be more or less serious depending on the circumstances and provides the Crown with discretion to choose the most appropriate procedure and range of potential penalties. For example, the offence of fraud under $5,000 -- one of the charges in this case -- can embrace criminal activity ranging from a young first offender switching price tickets on an item in a department store, to a repeat offender wrongfully appropriating the savings account of a vulnerable person under his or her care. The Crown prosecutor chooses the procedure that best fits the particular offence and offender. As this Court has recognized, discretion, including prosecutorial discretion, is an "essential feature of the criminal justice system" which will not be lightly interfered with…
R. v. Dudley,  S.C.J. No.58 at para. 65
…while it is without question that the Crown performs a special function in ensuring that justice is served and cannot adopt a purely adversarial role towards the defence…, it is well recognized that the adversarial process is an important part of our judicial system and an accepted tool in our search for the truth... Nor should it be assumed that the Crown cannot act as a strong advocate within this adversarial process. In that regard, it is both permissible and desirable that it vigorously pursue a legitimate result to the best of its ability. Indeed, this is a critical element of this country's criminal law mechanism… In this sense, within the boundaries outlined above, the Crown must be allowed to perform the function with which it has been entrusted; discretion in pursuing justice remains an important part of that function. (citations omitted)
R. v. Cook,  1 S.C.R. 1113 at para. 21
In exercising their discretion to prosecute, Crown prosecutors perform a function inherent in the office of the Attorney General that brings the principle of independence into play. Its fundamental importance lies, not in protecting the interests of individual Crown attorneys, but in advancing the public interest by enabling prosecutors to make discretionary decisions in fulfilment of their professional obligations without fear of judicial or political interference, thus fulfilling their quasi-judicial role as "ministers of justice”… Thus, the public good is clearly served by the maintenance of a sphere of unfettered discretion within which Crown attorneys can properly pursue their professional goals. (citations omitted)
Miazga v. Kvello Estate,  3 S.C.R. 339 at para. 47