Cheek Swabs for DNA Used to Look for Serial Killer:
An Orlando, Florida news station reports about a search for a serial killer using cheek swabs designed to test for a DNA match:
  Police officers in Daytona Beach are swabbing the mouths of persons of interests during traffic stops with special DNA kits in the hunt for an elusive serial killer, . . . . [T]he Daytona Beach police Chief, Mike Chitwood, said detectives have the killer's DNA.
  "Genetically, we know who he is," Chitwood said. "We have DNA evidence from the murder scenes — so, we got that. That is never going to go away. And, sooner or later, we will match the DNA to the physical person and bring closure to everything that is going on."
  Agents are using the DNA kits to collect as much DNA as possible during traffic stops and special operations in hopes on making a match.
  Local 6 showed agents stopping a person of interest from Canada, who gave his DNA to officers on the street using the DNA kit.
  The DNA kits are also being used in prostitution stings in the area.
  Hey, wait, you're wondering — can they do that? The story is short on details, so it's kind of hard to tell. But here's some background on the law, which will explain how the legal issues might go depending on how the facts play out.

  First, taking a DNA sample using a cheek swab is a Fourth Amendment search that would normally require a warrant. See Kohler v. Englade, 470 F.3d 1104 (5th Cir. 2006). It looks like the police don't have warrants here. The question then becomes if some exception to the warrant requirement applies to make the cheek swab reasonable. It may be that the officers are only asking targets for consent to give up a DNA sample. If that's the case, the swabs are constitutional under the consent exception. It also may be that the officers are only getting cheek swabs when they arrest someone. If that's right, the DNA samples are very probably constitutional under the search incident to arrest exception.

  On the other hand, if they aren't waiting until they arrest targets; aren't making the tests voluntary; and don't have particularized warrants, then these swabs are very likely unconstitutional. (There's some possible issues of exigent circumstances or special needs, but I tend to doubt they would work out.)

  Finally, it's worth flagging that I don't think the remedy is particularly clear in a case like this. Imagine an unconstitutional swab leads to a DNA match, and the target is then arrested. I gather that particular DNA match can't be used, as it's a fruit of the poisonous tree. On the other hand, I gather the police aren't blocked from trying to get a DNA sample some other way from the same guy, and since they know there's a match, presumably they would work hard to get another sample down the road anyway. DNA is not like a gun in someone's jacket pocket; it's always there, not just there at one particular time. It's not totally clear how the doctrine would work out, but presumably the police wouldn't just set the serial killer free — and presumably a court would let the government use another DNA sample taken another time in another way to prove the serial killer's guilt.