20. (1) Subject to this section, in any proceedings
for an offence under section 19 relating to pre-packed
goods, it shall be a defence for the person charged to
prove
(a)
that he purchased the goods from some other
person
(b)
(c)
(i) as being of the quantity which the
person charged purported to supply, or which
was stated in any invoice or similar document
relating to the purchase of the pre-packed
goods; or
(ii) as conforming with a statement marked on
the container of the pre-packed goods,
as the case may require;
that he so purchased the goods with a warranty
from that other person that they were of that
quantity or, as the case may be, did so conform;
that at the time of the commission of the offence
he had no reason to believe the statement
contained in the warranty to be inaccurate, that
he did in fact believe in its accuracy and, if
the warranty was given by a person who at the