James Palangio

The Crown appealed the respondent's acquittal on a charge of operating a motor vehicle with a blood alcohol concentration over 80 mg.

The trial judge had acquitted the respondent after accepting expert evidence that the absence of a value for 'uncertainty of measurement' raised a reasonable doubt about the proper functioning of the approved instrument.

The Superior Court of Justice allowed the appeal, finding that uncertainty of measurement is not required by law and that speculative evidence regarding potential instrument malfunction is insufficient to constitute 'evidence tending to show' under section 258(1)(c) of the Criminal Code.

A new trial was ordered.

The Court considered whether 2008 Criminal Code amendments limiting evidence to challenge breath test reliability applied to a trial concerning earlier events.

A majority held the amendments affected substantive rights because they eliminated the Carter defence as an independent route to raise reasonable doubt and therefore should not apply retrospectively.

The Court restored the trial acquittal and allowed the appeal.

A dissent would have treated the provisions as procedural evidentiary rules with immediate effect.