What is the test for committing an accused to stand trial at a preliminary hearing?

At the conclusion of the preliminary hearing the presiding judge is required to consider all of the evidence and to determine whether or not there is “sufficient” evidence to order the accused to stand trial: s.548 of the Criminal Code. It has long been held that this translates into a determination of whether or not there is some evidence on each essential element of the offence, such that a jury acting reasonably and properly instructed could convict: United States of America v. Sheppard 1976 CanLII 8 (SCC), [1977] 2 S.C.R. 1067, 30 C.C.C. (2d) 424. If such evidence exists the accused should be committed to stand trial. The preliminary hearing judge is not to otherwise assess the strength of the case or weigh conflicting inferences or assess credibility. Those tasks are for the trier of fact at a trial.