The goal of a robot should never be to kill a human being. Robots are not human police that are in danger of death, and therefore should never be equipped with lethal rounds. The goal of a robotic soldier or police patrolman would only be to disarm and detain. A robot would not be making judgement decisions about life and death because it is not also trying to protect its own life like a human soldier/policeman. There is no reason a robot could not simply detain a criminal until humans could arrive and arrest the suspect, there is no need for a robot to engage in lethal combat. I think the fears people have about robots swarming war zones and murdering civilians should be quelled by laws which prevent the construction of robots with lethal ammunition and the accountability of those that deploy robots if a robot does in fact kill a human being.
That's not completely true though, a large part of police work is also preventing violence against citizens. What would the robot do if it arrived at a domestic violence call and needed to save a women/child from abuse? I could see a massive public outcry if the robot simply watched the crime take place.
It would disarm and detain the assailant. The same thing a human police office ought to do in that situation. Are you trying to argue that it should just kill the abuser?
Certainly not in every case but there are a lot of times when disarming is not an option. I don't know if you have had any kind of defence training but I have and disarming an armed opponent is one of the hardest things to train for. More often than any one would like the police really have no choice.
