So there is a problem with assaults/murders on a street. Why not put cameras there to capture attacker's clearly, create super-harsh punishment for unprovoked a

So there is a problem with assaults/murders on a street. Why not put cameras there to capture attacker's clearly, create super-harsh punishment for unprovoked attacking, put a policeman on every corner, etc? How imposing laws against mixing alcohol in a shaker can is possibly related?