What is the test for an application to challenge for cause?

Any discussion of the accused’s right to challenge for cause begins with R v. Sherratt, 1991 CanLII 86 (SCC), [1991] 1 S.C.R. 509, where the accused was charged with murder and the application to challenge for cause was based on pre-trial publicity. L’Heureux-Dubé J., speaking for the 5 to 1 majority[1], started her analysis by noting that s. 638 places “little, if any, burden on the challenger” and that “while there must be an “air of reality” to the application, it need not be an “extreme” case…” (para. 63). She then went on to set out the test: 64 …The threshold question is not whether the ground of alleged partiality will create such partiality in a juror, but rather whether it could create that partiality which would prevent a juror from being indifferent as to the result. In the end, there must exist a realistic potential for the existence of partiality, on a ground sufficiently articulated in the application, before the challenger should be allowed to proceed.… (my emphasis)