Technology moves too fast for the law.  <i>Even if</i> police believe using a particular technology is unconstitutional, they are likely to use it anyway, because it will likely take years for a challenge to be brought to court, and definitely years to get to the highest (influential) courts.  Even after all this, the police will only have to stop the unconstitutional activity, and immunity will handle the rest.<p>States need to enact laws that will prevent police departments from using any new software without prior approval of their constituents (e.g. city council approval).