Significant Contributing Cause. R. v. Snowden
In R. v. Snowden (Ont CA, 2023) the Court of Appeal considered the 'significant contributing cause' form of causation, here in a criminal context:
 The sentencing judge’s approach to causation was unduly narrow in requiring that the respondent be the “root cause” of, or their actions in “direct causal connection” with, the severe psychological damage experienced by the victims. Moreover, the sentencing judge failed to consider not only whether the respondent’s conduct did “inflict severe psychological damage”, but also whether it was “likely to inflict severe psychological damage”, in accordance with Morgan (discussed in para. 64, above).. R v Singh
 Canadian criminal law has long recognized the different ways in which a person may cause harm to another. An individual may be the sole cause of another person’s harm, a co-perpetrator of that harm, or they may contribute to, or exacerbate, an existing harm.
 In Smithers v. The Queen, 1977 CanLII 7 (SCC),  1 S.C.R. 506, a homicide case, Dickson C.J. stated the test for causation as “a contributing cause of death, outside the de minimis range”: p. 519. A more modern formulation speaks of being a “significant contributing cause”: R. v. Nette, 2001 SCC 78,  3 S.C.R. 488, at para. 71 per Arbour J. and R. v. Maybin, 2012 SCC 24,  2 S.C.R. 30 at paras. 1, 5. Thus, for liability purposes, a person need not be the “root cause” or “direct cause” of a person’s harm. One may contribute to, or perpetuate, a harm that has already been caused by the actions of another. That harm may be different in nature.
In R v Singh (Ont CA, 2015), a criminal case against a landlord found to have caused the death of a tenant, the Court of Appeal endorsed the following definition of causation:
 As the trial judge correctly noted, the test for determining legal causation is whether the appellant’s conduct was a significant contributing cause of Mr. Dhaliwal’s death: R v. Nette, 2001 SCC 78 (CanLII),  3 S.C.R. 488, at paras. 69-72; R. v. Shilon, 2006 CanLII 41280 (ON CA), 240 C.C.C. (3d) 401,  O.J. No. 4896 (C.A.), at paras. 27, 30.