Personally, I disagree with mandatory minimums for these offences. But I particularly disagree with mandatory minimums in excess of that set out for the impaired driving simpliciter offence in cases resulting in death or injury.
The mandatory minimum penalty for impaired driving is a $1000 fine and a one-year driving prohibition. In cases where there is a death, the potential exists for life imprisonment. It is rare to see cases where individuals aren't sentenced to some lengthy term of imprisonment in cases of death. I mean, sure, we all heard about the individual who received 90 days in Chilliwack. But those sentences are the exception to the rule. Remember Carol Berner? She received 30 months upon conviction. Her sentence was appealed as being disproportionate, and was upheld on appeal. The Supreme Court of Canada refused leave to appeal the conviction.
The point is that the Courts of this country take these cases seriously. There is no need, in my view, to tie the hands of judges with mandatory minimums when the sentencing process is treated with the utmost solemnity and seriousness. Nobody in the justice system takes impaired driving deaths lightly. Sentences like the one imposed in Ms. Berner's case are upheld on appeal because they are within the range of sentences given to similarly situated offenders.
Jail time does very little to "solve" the problem of impaired driving. Just look at PEI, which has an informal policy of 3-day jail sentences on first conviction for impaired driving. And yet, they have one of the highest rates of impaired driving of all the provinces. And that rate of impaired driving incidents actually increased after the policy was implemented.
The goals of the sentencing process, as set out in Section 718 of the Criminal Code are not very well-served. Sure, general deterrence may be met. But nobody who drinks and drives sets out to injure or kill people. It's a by-product of the unlawful act that is generally not punished by jail time, and so jail sentences in death cases have little to do with deterrence from what I can tell. If PEI is any example, jail doesn't keep people from drinking and driving. Maybe it's the simply fact that alcohol impairs judgment, (See also: any Vine video, ever) which means that people who choose to get behind the wheel aren't necessarily thinking about the consequences. I think it's important to keep in mind that intoxication is a defence to most criminal acts (a notable exception being, of course, impaired driving.)
And so to bind the hands of judges, who see cases similar and different, and individuals of all backgrounds, with mandatory minimum sentences for the more serious impaired driving offences is something that really strikes a blow against the interests of justice. Judges are trained and capable of considering the particular circumstances of an offender and determining the appropriate sentence based on the principles of sentencing and the offender's circumstances. I trust that Parliament recognizes that, which is why these attempts to create mandatory minimums each time have failed.
I would trust, in any event, that there would be a Constitutional challenge to such provisions, similar to the recent challenge to the minimum sentence provisions for firearms offences.
EDIT: After writing this post, I found this story about a 10-year prison term for a man convicted of impaired driving causing death. The article, I think, highlights why this sentence was much longer than the average. And that, folks, is sentencing principles at work.