You'd go through the section 12 jurisprudence--I can give you the names of the cases, Smith, Gault, Morrisey, Ferguson--and you make your claim about gross disproportionality in terms of blameworthiness and the effects of punishment. The effects of punishment are front and centre under section 12. That's why you'd want evidence about deleterious effects of long-term punishment, which was not in front of the court in the 1990 basket of cases. They argued that 25 years is too long, and the Supreme Court said, well, no, it's the gravest punishment with the gravest penalty.
On November 4th, 2009. See this statement in context.