By Peter McCormick
If several judges on the Supreme Court of Canada suddenly sprouted two heads in their annual official photo, we would certainly take notice and would be looking for an explanation. But something similar has actually taken place in Supreme Court decisions without attracting either focused attention or a search for the reason why. More specifically – a significant number of Supreme Court decisions now routinely attribute judgments or minority reasons not to a single judge but to a pair (more rarely a trio) of judges. I leave aside for the moment the perhaps-not-unrelated phenomenon of the hydra-headed “By the Court” judgments, which have been around for longer but are rather less frequent; my focus here is on the more numerous examples of this narrower form of co-authorship.
The practice is frequent enough and important enough to deserve attention. Co-authored judgments are a recent development – the earliest significant example was R v Sparrow,  1 SCR 1075. It rose beyond the sporadic only in the closing years of the Lamer Court, becoming more frequent and more routine (multiple examples every year) for the McLachlin Court. To the Lamer Court’s 26 examples we can now add the 127 of the McLachlin Court and the 6 of the Wagner Court to date. Co-authorship involves minority reasons as well, with 46 examples for the Lamer Court, 72 for the McLachlin Court, and 11 for the Wagner Court. The total count is therefore 159 judgments and 129 sets of minority reasons in 30 years, for a Court that delivers about 60 reserved decisions a year. The practice only started in the late 1990s, but co-authorship has now become an ongoing feature of how the Supreme Court handles its business.
It might be suggested that perhaps the Court does this only for its more routine and less important decisions (although the count above already excludes the “from the bench” decisions that continue to make up about one-sixth of the caseload even after 1999 amendments limited appeals by right). As I have elsewhere demonstrated at some length, this “minor cases” reservation cannot be sustained. Co-authorships are used proportionately most often for constitutional cases (Charter, federalism and aboriginal cases alike) and public law cases, most often for cases that have drawn larger numbers of interveners, and most often for cases with higher subsequent citation frequencies. None of this says “routine” or “unimportant”.
Let me expand on this criterion of citation frequency. Several different factors bear on how often a case is cited by the Court in later decisions, but citation counts remain a useful indicator of the ongoing impact of a decision. More to the point, they provide a measure of how a specific judge’s influence endures beyond their own service on the Court, also showing the specific areas of law within which that persisting influence is the most important. These are useful indicators indeed for assessing a judicial career. It is therefore striking that the four most frequently cited decisions of the McLachlin Court (measured in “times cited per year since delivery” to level the playing field for the more recent decisions) are co-authored decisions; the four cases are Dunsmuir v New Brunswick, 2008 SCC 9, Housen v Nikolaisen, 2002 SCC 33, Bell ExpressVu v Rex, 2002 SCC 42, and R v Grant 2009 SCC 32. Three further cases (R v Jordan, 2016 SCC 27, Canadian Western Bank v Alberta, 2007 SCC 22, and Canada (Citizenship and Immigration) v Khosa, 2009 SCC 12) join them in the McLachlin Court “top ten.”
The blog of the Osgoode Hall law school TheCourt recently reinforced this point from another angle. In a “where are they now?” post about the ten most recently retired Supreme Court justices, they reminded us of each judge’s most frequently cited decision. For full half of them, including McLachlin herself, that involved a co-authored judgment. The practice of co-authorship is not at the margins; it is right at the center.
These two-headed decisions clearly matter; how are we to account for their emergence? There are several possible reasons, none of which provides a completely satisfactory answer.
One explanation might be an unusually close partnership between judges who agree extensively on a range of issues, such that close collaboration flows naturally from this recurring congruence of views. This description clearly captures Cory and Iacobucci, who effectively invented the practice in the late 1990s. During their shared service on the Court, they posted the highest level of two-judge agreement of any pairing of judges; it is reasonable to see co-authorship as growing from this fertile soil of extensive agreement. But this explanation does not work for the complex network that has emerged more recently – on the McLachlin Court, every single justice was involved in some degree of co-authorship, most with several different partners.
A slightly more systemic answer might couch it in terms of alliances on a court that tends to fragment along predictable lines, with co-authorship reinforcing the solidarity of both “in-group” and “out-group” in the face of its chronic adversaries. But this explanation does not work either, simply because the network has been so extensive – there were no fewer than 45 different combinations of two or three judges who produced co-authored judgments on the McLachlin Court (slightly more if we extend the count to minority reasons). This is “bloc-eroding” behavior rather than “bloc-reinforcing” behavior.
A third explanation might be that it salvages a strong majority decision from multiple possible defections to an emerging separate concurrence. In a private conversation some years ago, a former justice of the Supreme Court explained his own participation in at least some co-authorships in precisely these terms. This would make co-authorship part of the reason for McLachlin’s success in sharply reducing the frequency of separate concurrence compared with the preceding Lamer Court. This is perhaps mildly problematic given that such compromise can involve less a genuine meeting of minds than a degree of calculated ambiguity on central points of disagreement and a careful avoidance of problematic subsidiary issues; at least co-authorship does the service of highlighting this possibility.
A fourth explanation might be that it has a socializing function, with co-authorship linking established members of the Court with more recently appointed colleagues. Even for experienced judges elevated from provincial courts of appeal, the transition to the Supreme Court can be daunting. However, such a disparity of experience between a pair of co-authors is much too infrequent to make this a pervasive explanation, although it may sometimes be a factor.
A fifth explanation might be that it sometimes represents an ambitious attempt to solve very large and deep-rooted problems in the Court’s jurisprudence. The obvious example is Dunsmuir, with its ambitious recasting of the standards of review for administrative tribunals. Double Aspect, in cooperation with the Administrative Law Matters blog, published an extended multi-part discussion of the case on its tenth anniversary last year. Not only the most frequently cited decision of the McLachlin Court, it is also the most widely criticized; this and other blogs continually share expectations (which are just as continually frustrated) that some current case before the Court will provide the opportunity to revisit and adjust the Dunsmuir precedent, but this makes the point about how ambitious the undertaking was.
The search for a “why” is complicated by the fact that we do not even know the “when” of the formation of the writing partnership. Does it occur spontaneously during the post-hearing judicial conference, with the initial assignment of the writing of majority reasons? Nothing in the descriptions of this process either specifically mentions or specifically excludes the possibility of a joint assignment, and in a recent interview McLachlin suggested that at least some co-authorships emerge this way. Or does it occur after such an assignment, during the “circulate and revise” process and possibly under some prodding from the Chief Justice, like the salvage efforts described above? Clearly, this sometimes happens as well, but nothing in the physical appearance of the decision in the Supreme Court Reports gives any real hint as to which happens how often.
The benefit of the co-authorship practice is clear: it results in a more genuinely and visibly collegial court that presents an institutional face rather than an individualist one, that emphasizes pervasive agreement rather than division, that shows us a Court of persuasion and cooperation rather than polarization. As practised by the McLachlin Court, it eliminated the predictable blocks of the Lamer Court. Recall the “gang of five” who dominated the Court’s most important decisions for much of the 1990s, with the other judges (most notably L’Heureux-Dube and McLachlin) obliged to do much of their own writing in minority reasons. No such persisting fragmentation has been seen for the past twenty years. There was more to the McLachlin Court’s unity and collegiality than co-authorship, but co-authorship was definitely part of it.
However, such benefits are always purchased at a price. For one thing, it is harder for lower courts or academics to unravel the nuances. We can sometimes clear up some ambiguities in the wording of a judgment by comparing the immediate decision with earlier reasons written by the same judge, or we can track the evolution of a judge’s thinking (with hints of where it might go next) by seeing how it is cited and applied in the same judge’s later reasons. This becomes more difficult if we cannot be sure which of a pair of judges might have written the particular passage or might be making the later citation. By the same token, the device depersonalizes the decision and diffuses the assignment of criticism or blame.
For another, it undercuts the venerable common law tradition of accountability, of the clear responsibility of the specific individual judge to which those reasons are attributed. This is already attenuated by the “circulate and revise” procedures of the Supreme Court, such that a collegial dimension already pervades the final version – but even if we are looking at “lead authorship” rather than genuine “solo authorship”, the accountability dimension is real, and traditionally it has been important. It is clearly eroded by a pervasive co-authorship practice focused on the Court’s more important (in terms of subject matter), more controversial (in terms of interveners), and more influential (in terms of citation counts) decisions.
Where is co-authorship taking us, and should we welcome the journey? The next time a two-headed judge raises its head in the Supreme Court Reports, these are the questions to ponder. We can debate whether it is taking us to a better place, but it is certainly taking us to a different place, all the more intriguing because no comparable court seems to be embarking on anything similar.
 Shameless plug: to know more about “By the Court’ judgments, keep an eye out for a fall 2019 UBC new release entitled By the Court: Anonymous Judgments at the Supreme Court of Canada.
 Or, one might suggest, Irwin Toy in 1989, although I have been assured that this was actually a “By the Court” judgment that “went sideways” at the last moment rather than an intentional three-judge-shared set of reasons.
 Peter McCormick, “Duets, Not Solos: The McLachlin Court’s Co-Authorship Legacy” Dalhousie Law Journal, Vol. 41 (2018), 479.
 Mitchel Lasser makes this point very forcefully in his excellent Judicial Deliberations: A Comparative Analysis of Transparency and Legitimacy (OUP, 2004)