All lives are not equal. The value of the life of a thief whose only impact on the society is negative, cannot be compared to e.g. a doctor.
Do you also define yourself according to the worst thing you've ever done?
So why would someone risk his live and become a thief instead of a doctor?
I agree with the general concept, but it's not practical to use.
What about a bad medic? Or a thief that helps homeless people in their free time?
If it was easy, we would have simpler laws and better justice systems...