What is the test for an expert opinion in a patent?

As noted in Whirlpool at para. 53, the words used in a patent must be looked at and understood “through the eyes and with the common knowledge of a worker of ordinary skill in the field to which the patent relates.” This enables the reader to appreciate the nature and description of the invention on a technical level. Consequently, in construing the claims, a judge may be assisted by expert witnesses. However, a judge is not bound by the opinion of any expert. A judge’s assessment of the expert evidence will not be reversed on appeal absent palpable and overriding error: Halford v. Seed Hawk Inc. 2006 FCA 275, 54 C.P.R. (4th) 130 at para. 11; Weatherford at para. 24. First issue: Did the Judge err in holding that the rear cross piece of the landing gear disclosed in the ‘787 Patent must be vertical or substantially vertical?