What is the standard of proof respecting gross negligence and the reference to the provision imposing a penal sanction?

The standard of proof respecting gross negligence and the reference to the provision imposing a penal sanction were discussed by Cattanach J. in Udell v. M.N.R., [1970] Ex C.R. 176. At page 190, in discussing subsection 56(2), now subsection 163(2) of the Act, he provided the following comments: There is no doubt that section 56(2) is a penal section. In construing a penal section there is the unimpeachable authority of Lord Esher in Tuck & Sons v. Priester [(1887) 19 Q.B.D. 629] to the effect that if the words of a penal section are capable of an interpretation that would, and one that would not, inflict the penalty, the latter must prevail. He said at page 638: We must be very careful in construing that section, because it imposes a penalty. If there is a reasonable interpretation which will avoid the penalty in any particular case we must adopt that construction.