Police response times will never be low enough to be physically preventative outside of special areas (airports, stadiums, high traffic areas). It doesn't take

Police response times will never be low enough to be physically preventative outside of special areas (airports, stadiums, high traffic areas). It doesn't take that long to mug somebody. Police violence is more of a way to discourage wrongdoing on the part of rational actors. Irrational actors (terrorists, mentally ill, drug-addled, enraged, desperate) probably won't be affected short of an oppressive police state.