What is the common law definition of joint authorship in Canada, England and the United States?

In my opinion, the common law definition of joint authorship, the statutory definitions of joint authorship in Canada, England and the United States, and the judicial interpretation of the statutory definitions all confirm that mutual intent is a prerequisite for a finding of collaboration. As to the importation of the requirement of an intent to co-author into Canadian copyright law, plaintiff's counsel's position on the court's findings in Childress v. Taylor was that given the legislative history behind the definition of "joint work," and the unique jurisprudence which flowed from the definition, that case should not be relied upon to determine the test for joint authorship in Canada. I disagree with this position. I have concluded that the intent to co-author requirement mandated by the Childress v. Taylor line of cases should be part of the test for joint authorship under s. 2 of the Act for the reasons that follow.