Suppose some doped-up burglar tries your door, finds it locked, and leaves behind traces of drugs on the knob? You report an attempted burglary, the cops test the knob, and you get arrested? This lowers my respect for the cops a little more, and it was pretty low to start with.
The doorknob was only a peice of the compelling information that convinced a judge to issue a search warrant. The perp was arrested after a properly executed search turned up illegal drugs.