Causation in homicide: the impugned act must be a "significant contributing cause" of death

R. v. Belisle, 2012 ONCA 303 is a good current source for the test for causation in homicide:

 

[30]       A single test – the Smithers test – for causation applies to all forms of homicide:  the impugned act must be a “significant contributing cause” of death, beyond something trifling or minor: see R. v. Nette, 2001 SCC 78, [2001] 3 S.C.R. 488, at paras. 71-72.