As a general proposition, a person is not legally responsible for a contravention of
a law if, at the time of the contravention, that person was subject to a defect of mind
that is recognised by law as sufficient to relieve him or her of responsibility for his
actions (Gardiner and Landsdown 1939:30). The taxpayer, depending on the
severity of the defect of the mind, may plead such a reason as a defence or as an
“extenuating circumstance” for the purposes of section 76 of the Act.
However, for this defence to succeed, there should be some evidence that the
disability of the mind was an operative cause of the failure to comply with the Act.
This will be difficult to demonstrate when the surrounding evidence establishes that
the accused otherwise functioned well in the business world.