You can be sure that bad people as well as good cops will be taking note of how easy it is to cut through UPVC, Solid Timber and even modern high security composite doors with a chainsaw. Probably to best way to prevent this happening to your door AFTER TSHTF is to think about cladding the door with a steel sheet on the inside or drilling horizontally into the edge of the door in multiple places and expoxying some steel rods into the holes. the door will lok no different from the outside but any change saw access with quickly be stopped.
http://www.dailymail.co.uk/news/article-...conds.html