That anybody here would even consider that it is right, meet, and moral for agents of the government to, in secret and without your consent, run laboratory tests on the residues on your front doorknob, regardless of whether you live in slumville or Couer de Lage Estates, without so much as a by-your-leave from you, a judge, or anyone else, is appalling.
"Expectation" of privacy?!?
Yeah, I have a pretty dang good expectation that Joe Blow the Civil Servant is not going to come along with his lab kit and gas chromatograph and play Pointdexter with my front door or any other part of my domicile. I don't care if my doorknob is set behind three belts of concertina wire, or sticks out into the sidewalk, it's my doorknob. Keep your frickin' hands off.
(How come when a lowly citizen peers through my window at night, he's a Peeping Tom, but when the police do it, it's the "Plain View Exception"?)