“In terms of the protection of society, [isolation/imprisonment] is the option of last resort. Even as such, it suffers from the ultimate weakness that if the fundamental requirement of proportionality* is observed, the individual concerned must eventually be released from jail. Experience teaches us that most people emerge from prison a worse threat to society than when they entered. Thus care and restraint must be exercised when imposing a sentence of imprisonment even when the goal is to isolate the offender.” ~Justice of Appeal Wood. in R v Sweeney (1992), 11 C.R. (4th) 1, 71 C.C.C. (3d) 82, 1992 CarswellBC 460 (BC Court of Appeal)
*fundamental requirement of proportionality, put less eloquently, is the idea that “the punishment fits the crime”. It can also encompass the idea that a penalty should be proportional to the “aims” or desired outcome of the penalty, and not excessive.