In R. v. O’Connor,
 4 S.C.R. 411, a majority of the Supreme Court of Canada had recognized that the common law abuse of process doctrine has essentially been subsumed within Charterbreach analysis under section 7. Principles of fundamental justice both reflect and accommodate the common law doctrine of abuse of process such that there is no utility in maintaining two distinct analytic regimes: O’Connor, at paras. 70-71.
A stay of proceedings is the most drastic remedy a criminal court can order (R. v. Regan, 2002 SCC 12 (CanLII),  1 S.C.R. 297, at para. 53). It permanently halts the prosecution of an accused. In doing so, the truth-seeking function of the trial is frustrated and the public is deprived of the opportunity to see justice done on the merits. In many cases, alleged victims of crime are deprived of their day in court. In some sense, an accused who is granted a stay under the residual category realizes a windfall.
Nonetheless, there are rare occasions —the “clearest of cases” — when a stay of proceedings for an abuse of process will be warranted (R. v. O’Connor, 1995 CanLII 51 (SCC),  4 S.C.R. 411, at para. 68). These cases generally fall into two categories:
(1) where state conduct compromises the fairness of an accused’s trial (the “main” category); and
(2) where state conduct creates no threat to trial fairness but undermining the integrity of the judicial process (the “residual” category).
O’Connor, at para. 73; R. v. Babos, 2014 SCC 16,  1 S.C.R. 309, at para. 30,31.
Reserved for the clearest of cases
As the authorities repeatedly emphasize in connection with both the main and residual categories of abuse of process, stays of proceedings are rare, reserved for the “clearest of cases”. In the residual category, stays are “exceptional” and “very rare”: Tobiass, at para. 91; Babos, at para. 44; See also R. v. Conway,  1 S.C.R. 1659, at p. 1667
Indeed, in the residual category, cases warranting a stay of proceedings will be “exceptional” and “very rare” (Tobiass, at para. 91). But this is as it should be. It is only where the “affront to fair play and decency is disproportionate to the societal interest in the effective prosecution of criminal cases” that a stay of proceedings will be warranted (R. v. Conway, 1989 CanLII 66 (SCC),  1 S.C.R. 1659, at p. 1667); Babos, at para. 44
A Prospective remedy
A stay of proceedings is a prospective remedy. It does not redress a wrong that has already been done. Rather, the stay aims to prevent the perpetuation of a wrong that, if left alone, will continue to trouble the parties and the community in the future. Just because the state has treated a person shabbily in the past does not, without more, entitle that person to a stay of proceedings. The evidence must also make it appear that the state misconduct is likely to continue in the future, or that carrying forward with a prosecution will offend society’s sense of justice.
R. v. Gowdy, 2016 ONCA 989 at para 70; Babos, at para. 36; Canada (Minister of Citizenship and Immigration) v. Tobiass,  3 S.C.R 391, at para. 91.
The Legal Test for a Stay of Proceedings
The test used to determine whether a stay of proceedings is warranted is the same for both main and residual categories of abuse of process and consists of three requirements:
1. prejudice to the accused’s right to a fair trial or the integrity of the justice system that will be manifested, perpetuated or aggravated through the conduct of the trial or its outcome;
The first requirement recognizes that there are limits on the type of state conduct society will tolerate in the prosecution of offences. Sometimes, state conduct will be so disturbing that having a trial, even a fair trial, will leave the impression that the justice system condones conduct that offends society’s sense of fair play and decency. The question that requires answer in connection with the first requirement is whether proceeding to trial in light of the state conduct would do further harm to the integrity of the justice system: Babos, at paras. 35, 38.
2. no alternative remedy capable of addressing the prejudice;
For the second requirement, the question is whether any other remedy short of a stay is capable of redressing the prejudice. Since the prejudice with which we are concerned in the residual category is prejudice to the integrity of the justice system, remedies must be directed towards that harm. In this category, we do not furnish redress to an accused for a past wrong done to him or her. Rather, we focus on whether an alternate remedy, short of a stay, will adequately disassociate the justice system from the impugned state conduct going forward: Babos, at para. 39
3. where uncertainty persists after requirements 1 and 2 have been considered, whether the interests in favour of granting a stay prevail over society’s interests in having a final decision on the merits.
The third requirement – a balancing of interests – is of great significance in the residual category. Balancing is only required when uncertainty remains after consideration of the first two requirements. What the court is asked to decide is which of two options – staying proceedings or holding a trial – better protects the integrity of the justice system. Relevant factors include but are not limited to:
the nature and seriousness of the impugned conduct;
the isolated or systemic and ongoing nature of the conduct;
circumstances of the accused;
the charges faced by the accused; and
the interests of society in having the charges determined on their merits: see Babos, at para. 41.