From the decision:

Justice Wagner wrote as follows (at paras. 1-6, 54, 61, 80-82, 87, 92, 138, 166-168):

"The repute of our criminal justice system rests on the deeply held belief of Canadians that the right to liberty and the presumption of innocence are fundamental values of our society that require protection. However, that repute also depends on the confidence citizens have that persons charged with serious crimes will not be able to evade justice, harm others or interfere with the administration of justice while awaiting trial. The risk that one of these events might tarnish the repute of the justice system was recognized by Parliament in enacting s. 515(10) (a) and (b) of the Criminal Code, R.S.C. 1985, c. C‑46 (“Cr.C .”), under which the interim detention of an accused may be ordered where that is necessary to ensure the attendance of the accused in court or to guarantee the protection or safety of the public.

Moreover, Parliament judged that there are circumstances in which releasing an accused person could undermine the repute of the justice system, and this led it to provide, in s. 515(10) (c) Cr.C., for a third ground for interim detention, maintaining confidence in the administration of justice. Thus, Parliament recognized that there are circumstances in which allowing a person charged with a serious crime to be released into the community pending trial in the face of overwhelming evidence might suggest to the public that justice has not been done: see R. v. Hall, 2002 SCC 64, [2002] 3 S.C.R. 309, at para. 26.

This appeal affords the Court an opportunity to consider the circumstances in which pre‑trial detention of an accused is necessary in order to maintain the confidence of the Canadian public in the administration of justice in accordance with s. 515(10) (c) Cr.C. This provision has already been considered by the Court in Hall, but the central issue in that case was the constitutionality of this ground for detention as it was worded at that time. In cases decided by lower courts since Hall, the provision has been given widely varying interpretations, making it necessary for the Court to provide further guidance on its application.

The ground for detention in s. 515(10) (c) Cr.C. requires that an effort be made to strike an “appropriate balance between the rights of the accused and the need to maintain justice in the community”:Hall, at para. 41. In addition, judges must adopt the perspective of the public in determining whether detention is necessary. What the word “public” means is not always easy to understand. These difficulties no doubt explain why s. 515(10) (c) Cr.C. has generated so much discussion among legal experts and led to inconsistent results across the country.

In my opinion, the scope of s. 515(10) (c) Cr.C. has been unduly restricted by the courts in some cases. This ground for detention is not necessarily limited to exceptional circumstances, to the most heinous of crimes involving circumstances similar to those in Hall, or to certain classes of crimes. The interpretation of s. 515(10) (c) Cr.C. has also been truncated by a misunderstanding of the meaning of the word “public” used in the provision’s French version (and implied in the word “confidence” used in the English version), which I will discuss below. For now, I will simply note that the “public” are reasonable, well‑informed members of the community, but not legal experts with in‑depth knowledge of our criminal justice system.

This appeal is the first time this Court has been called upon to determine the extent of the power provided for in ss. 520 and 521 Cr.C . to review decisions with respect to detention or to interim release. Since a decision whether to order the pre‑trial release of an accused involves a delicate balancing of all the relevant circumstances, the power of a judge hearing an application under s. 520 or 521 Cr.C . to review such a decision is not open‑ended. I conclude that exercising this power will be appropriate in only three situations: (1) where there is admissible new evidence; (2) where the impugned decision contains an error of law; or (3) where the decision is clearly inappropriate. In the last of these situations, a reviewing judge cannot simply substitute his or her assessment of the evidence for that of the justice who rendered the impugned decision. It is only if the justice gave excessive weight to one relevant factor or insufficient weight to another that the reviewing judge can intervene.

…

In conclusion, the application of s. 515(10) (c) is not limited to exceptional circumstances, to “unexplainable” crimes or to certain types of crimes such as murder. The Crown can rely on s. 515(10) (c) for any type of crime, but it must prove — except in the cases provided for in s. 515(6) — that the detention of the accused is justified to maintain confidence in the administration of justice.

…

Without drawing up an exhaustive list of possible circumstances surrounding the commission of the offence that might be relevant under s. 515(10) (c), I will mention the following: the fact that the offence is a violent, heinous or hateful one, that it was committed in a context involving domestic violence, a criminal gang or a terrorist organization, or that the victim was a vulnerable person (for example, a child, an elderly person or a person with a disability). If the offence was committed by several people, the extent to which the accused participated in it may be relevant. The aggravating or mitigating factors that are considered by courts for sentencing purposes can also be taken into account.

…

In short, the person in question in s. 515(10) (c) Cr.C. is a thoughtful person, not one who is prone to emotional reactions, whose knowledge of the circumstances of a case is inaccurate or who disagrees with our society’s fundamental values. But he or she is not a legal expert familiar with all the basic principles of the criminal justice system, the elements of criminal offences or the subtleties of criminal intent and of the defences that are available to accused persons.

It is of course not easy for judges to strike an appropriate balance between the unrealistic expectations they might have for the public on the one hand, and the need to refuse to yield to public reactions driven solely by emotion on the other. This exercise may be particularly difficult in this era characterized by the multiplication and diversification of information sources, access to 24‑hour news reports and the advent of social media.

Canadians may in fact think they are very well informed, but that is unfortunately not always the case. Moreover, people can also make their reactions known much more quickly, more effectively and on a wider scale than in the past, in particular through the social media mentioned above, which are conducive to chain reactions. The courts must therefore be careful not to yield to purely emotional public reactions or reactions that may be based on inadequate knowledge of the real circumstances of a case.

…

I would summarize the essential principles that must guide justices in applying s. 515(10) (c) Cr.C. as follows:

• Section 515(10) (c) Cr.C. does not create a residual ground for detention that applies only where the first two grounds for detention ((a) and (b)) are not satisfied. It is a distinct ground that itself provides a basis for ordering the pre‑trial detention of an accused.

• Section 515(10) (c) Cr.C. must not be interpreted narrowly (or applied sparingly) and should not be applied only in rare cases or exceptional circumstances or only to certain types of crimes.

• The four circumstances listed in s. 515(10) (c) Cr.C. are not exhaustive.

• A court must not order detention automatically even where the four listed circumstances support such a result.

• The court must instead consider all the circumstances of each case, paying particular attention to the four listed circumstances.

• The question whether a crime is “unexplainable” or “unexplained” is not a criterion that should guide the analysis.

• No single circumstance is determinative. The justice must consider the combined effect of all the circumstances of each case to determine whether detention is justified.

• This involves balancing all the relevant circumstances. At the end of this balancing exercise, the ultimate question to be asked by the court is whether detention is necessary to maintain confidence in the administration of justice. This is the test to be met unders. 515(10) (c).

• To answer this question, the court must adopt the perspective of the “public”, that is, the perspective of a reasonable person who is properly informed about the philosophy of the legislative provisions, Charter values and the actual circumstances of the case. However, this person is not a legal expert and is not able to appreciate the subtleties of the various defences that are available to the accused.

• This reasonable person’s confidence in the administration of justice may be undermined not only if a court declines to order detention where detention is justified having regard to the circumstances of the case, but also if it orders detention where detention is not justified.

…

For the reasons that follow, I am of the opinion that ss. 520 and 521 Cr.C . do not confer an open‑ended discretion on the reviewing judge to vary the initial decision concerning the detention or release of the accused. Nonetheless, they establish a hybrid remedy and therefore provide greater scope than an appeal for varying the initial order.

…

If the new evidence meets the four criteria for admissibility, the reviewing judge is authorized to repeat the analysis under s. 515(10) (c) Cr.C. as if he or she were the initial decision maker. The reviewing judge must therefore consider all the circumstances of the case, focusing in particular on the circumstances specified in that provision. The judge must then undertake a balancing exercise and determine, from the perspective of the public, whether the detention of the accused is still justified. The Palmer criteria, modified as I have just done, must not be applied in a manner that delays or needlessly complicates the release process. As I explained above, that process, by its very nature, generally requires an expeditious and flexible procedure. The criteria therefore serve as guidelines for the reviewing judge, but they must not have the effect of creating a procedural straightjacket that would interfere with the administration of justice.

…

In short, I find that, when all the relevant circumstances are weighed as required by s. 515(10) (c) Cr.C., the detention of the respondent was necessary to maintain confidence in the administration of justice.

I believe that a reasonable member of the public who, although not a legal expert, is nonetheless properly informed about the philosophy underlying the legislative provisions, Charter values and the actual circumstances of the case would not understand why the respondent should not remain in custody pending his trial. Such members of the public are not people who would allow themselves to be guided by their emotions and to be swayed by the mob or by incomplete or distorted information. In the face of such a brutal attack that was committed by several people in the middle of the night against a bus driver, a person who was serving the community, and that had serious consequences for the victim’s health and integrity and was captured on a videotape that left no doubt as to the respondent’s active participation in the assault, I believe that the confidence in our justice system of a reasonable member of our society would be undermined if the interim detention of the respondent were not ordered.

I would allow the appeal. It was not open to the Superior Court judge to interfere with the initial release decision, and he unduly restricted the scope of s. 515(10) (c) Cr.C. and erred in basing his decision on the question whether that the offence was “unexplainable”. The detention of the respondent is justified on the basis of s. 515(10) (c) Cr.C. The detention order is accordingly restored."

Note: This is drawn from Eugene Meehan’s SupremeAdvocacy Weekly Updates for the Law Community.