In nations that have just experienced a civil war in which unrest is still palpable and dangerous, sometimes police force is needed in order to keep the citizens safe. Order and people directly in charge can be good things in order to calm situations down enough in order for better forms of government to take effect. If madness is happening in the streets when a new government tries to take control, it probably won't last long. So yes, a police state can sometimes be justified.
No, a police state that controls every step of its citizens cannot be justified. People must be free. Personal freedom is one of the basic, fundamental human rights. With that being said, any state should have laws, and these laws must be strictly followed and enforced. Freedom does not mean lawlessness.