I argue that of all things, law should be as deterministic as possible.
I've always thought that we (as a country) should maintain one single ordered list of specific crimes and punishments. Every new case that wants to set a punishment must insert it into this ordered list and explain convincingly why it fits into the list at the proposed position.
This would prevent the outrageous differences we see today where someone gets a few days of house arrest for murder and another guy gets a decade of solitary confinment for stealing a pen.