What is the test for recovery of damages in a construction accident where a piece of iron falls from a structure and strikes a person lawfully in the lane?

I agree with the learned trial Judge, and for the reasons given by him, that the respondent is entitled to recover. This main branch of the case admits, I think, of little doubt. A building is being erected on a city lot immediately abutting on a public lane. A piece of iron used in the building operations falls from the structure and strikes a person lawfully in the lane. These circumstances cast upon the defendants the duty of showing that there was no negligence (Byrne v. Boadle, 2 H. & C. 722, 33 L.J. Ex. 13, at p. 16). They endeavour to do this by adducing expert evidence to the effect that the plans of the building and the methods of workmanship followed were the best known to the trade. Here they are not by the expert witnesses of the plaintiff (and I refer particularly to McKay, an experienced builder), who show that a much safer method might and should have been adopted, and is in fact adopted in practice. This evidence is of the clearest kind and is accepted by the trial Judge, and, indeed, it is difficult for me to see how he could have rejected it. On such a state of facts the plaintiff is undoubtedly entitled to a verdict.