Orin Kerr isn't so sure:
After comparing cheek swabs with other searches requiring only reasonable suspicion, we conclude that the DNA sample collection technique at issue here, although minimally invasive, is also one of those limited searches that requires only reasonable suspicion and may therefore be conducted without a warrant. If anything, the cheek swab involves much less impact on the subject than some other searches that all agree may be conducted based on mere reasonable suspicion. As the United States Supreme Court has observed, “[e]ven a limited search of the outer clothing for weapons constitutes a severe, though brief, intrusion upon cherished personal security, and it must surely be an annoying, frightening, and perhaps humiliating experience.” Terry, 392 U.S. at 24-25. And yet, it is universally understood that such a pat-down may be conducted upon reasonable suspicion.
In contrast, a cheek swab takes even less time than a pat-down or field sobriety tests (”FSTs”) and is painless. Moreover, a swab of the inside of the cheek is very limited in scope, whereas a pat-down will generally involve manual exploration of the entirety of a suspect‘s body, including the genital areas. Finally, a swab does not carry nearly the same potential for opprobrium as pat-downs or FSTs, which will typically occur on public thoroughfares. As such, swabs are even less violative of the “[t]he interests in human dignity and privacy which the Fourth Amendment protects” than pat-downs or FSTs.
I agree with Orin -- the DNA swab is most certainly a search for evidence, not something done for officer safety. It is not the physical intrusiveness that makes it bad, but the invasiveness of the information obtained. Under current American law, a search for evidence should only be done with a warrant or under certain exceptional circumstances (such as when police are in 'hot pursuit' of a suspect and fear the destruction of evidence). While a DNA swab doesn't fit under any of these existing paradigms, I'd also have to agree with Orin that it is difficult to predict what the Supreme Court would decide on this. If it is upheld, I'm concerned that it could set a precedent that leads to a weakening of Fourth Amendment rights and expose police officers to greater risk of violence during routine car stops.
Maybe, but I’m not so sure. First, the rule allowing pat-downs is an exception to the usual rule to account for the specific interest in officer safety. The pat-down search can only be for weapons, not evidence: The reasonable suspicion is that the suspect is armed and dangerous, not that he has evidence on his person. In contrast, a DNA test is obviously for evidence, not for officer safety. If the general rule is that a search of a person requires probable cause and a warrant, I’m not sure why a DNA test isn’t part of the usual rule.
It’s true that some courts have permitted field sobriety tests and fingerprinting based on reasonable suspicion, but I have understood those cases to be about seizures, not searches. The Terry stop power allows a relatively broad authority to temporarily seize a person based on reasonable suspicion, but there’s a difference between allowing a seizure to control the scene and allowing a search of a person’s body.
I suspect that eventually the Supreme Court will have to decide this issue: There isn’t a circuit split on it yet, as far as I know, but my understanding is that district courts and intermediate state courts are divided. Eventually the issue will work its way up to the Supreme Court, although I think it’s hard to predict what the Court would do.