And there have been home breakins in my area where they theives wear black jumpsuits "scream" police and flash phony badges and by the time people figured out it wasn't the cops, it was too damn late.
If cops are going to do breakins (no knock searches), there is an added responsibility on their part to be 100% sure they have the right address. These mistakes happen far too often. This isn't like knocking on the wrong door serving a search warrent. Innocent people have been injured and killed many times in these things.
If possible, as Claire whatserface has advised, harden your house to the point where you can actually call 911 to ask if this is police before they get in.