What is the legal test for spoliation?

In Canada, the leading authority is St. Louis v. The Queen (1895), 1896 CanLII 65 (SCC), 25 S.C.R. 649 where the presumption arising against a government contractor for destruction of books and documents which might have supported its claim was held to have been rebutted by the oral evidence of the contractor's employees, who testified as to their knowledge of the facts contained in the destroyed documents. It was further noted that spoliation is an evidentiary rule that raises a presumption, and not an independent tort.