No one is a criminal until convicted as such by a jury of their peers.
You might want to rethink this. Crimes are committed by criminals, yet many criminals are never caught, the absense of a conviction does not mean the crime did not occur. Additionally, some criminals are neither charged nor convicted, we had one in the Oval Office a few years back.
As one of the people trying to mitigate the Salem Witch Trials said roughly, "It is better for 100 witches to get away than for one innocent to be convicted."
It should be the same with today's murders etc. If people are not caught but one innocent is protected, so be it.