R. v. McDonald
2008 ONCJ 536 (CanLII),  O.J. No. 4297
Paragraph 5: "The old law always permitted the defence to call evidence with respect to malfunction or error in the breath machine or its operation and in fact in R v Gilbert (1994) 92 CCC 3d 466 the Court of Appeal said that a Carter defence without such evidence might encounter difficulties in being accepted (though in practice, a bare-bones Carter often succeeded). Bill C2 made a requirement of what formerly was merely desirable from a defence standpoint."