(1) The following special pleas, and no others, may be pleaded in accordance with the relevant provisions of this Sub-Part, that is to say—
(a) a plea of autrefois acquit;
(b) a plea of autrefois convict;
(c) a plea of pardon, and such plea under section 327 with respect to defamatory libel.
(2) All other grounds of defence may be relied on under the plea of not guilty.