What is the test for a plea of justification in a libel action?

I am of the view that there is a distinction to be made between the line of cases following Scott v. Sampson and the present case. The defendants do not seek, by the introduction of evidence of the specific acts identified in the court file, to bring in evidence extrinsic to the libel, in an effort to show that the plaintiff ought not to enjoy the reputation he has. They are attempting to introduce evidence to prove that the very acts of which they published details, and of which the plaintiff complains, were committed. There is, clearly, fundamental disagreement over whether the plea of justification should succeed. The defendants suggest that the variation between what was published to have been the facts and what were the actual facts was relatively insignificant, while the plaintiff submits that the untruths were egregious. I do not see how this court can fairly assess that issue without permitting evidence of the actual facts concerning which the words complained of were published, to be compared to what was, in fact, published.