While individual examples of crime and murder are upsetting and are certainly abused by politicians to gain more power, they are actually a small cause of death and they don't justify destroying privacy.
Not to mention that as far as I am concerned, even someone e.g. breaking into a house - not speaking of violent crime - is far more damaging and traumatizing than some random cop looking up his exes license plate and doing nothing with it. Even if the numbers of instances were comparable.