As the talking heads, politicians and others complained about the violations to our privacy at the hands of the NSA (what did these people think they were doing), the Supreme Court decided a case involving the Fourth Amendment and the decision went relatively unnoticed.
In a 5-4 decision (interestingly the dissent was Scalia, Kagan, Sotomayor and Ginsburg), the Supreme Court decided, in Maryland v. King , that there was no 4th Amendment violation when the state of Maryland took a DNA sample of an individual who had been arrested for a serious crime, but had yet to be convicted and then processed that sample and ran it through CODIS.
Let me quickly go through the facts of the case. Alonzo King was arrested on charges of first and second degree assault for menacing a crowd with a firearm. In the process of booking King, they took a swab to his inner cheek for DNA. That is the statutory practice in Maryland where all those arrested on major crimes will have their DNA collected. The DNA will be processed only after arraignment and will be destroyed if the defendant is not convicted of the crime. At the same time, the DNA will be ran through the FBI's CODIS database. A few weeks after Maryland had collected King's DNA, they discovered, after sending the DNA through CODIS, that it was a match to DNA found in an unsolved rape case. King was charged with the rape and during the trial moved to have the DNA tossed out because it was discovered in violation to his 4th Amendment rights.
The Supreme Court disagreed. The majority balanced the intrusiveness of the search with the State's interest in conducting the search (incident to an arrest). Basically, the majority found a great interest in collecting and running the DNA through CODIS in order to identify the individual. The identity of the individual includes whether that person committed or is suspected of committing any past crimes. Further, knowing these past potential crimes is important because a person who is committed other crimes is more likely to flee. (That makes no sense - if all the police has is DNA, a person is not likely to flee if the police do not get his DNA.) The majority then balanced that against the minor intrusiveness of the procedure (a swab on the cheek) and the fact that CODIS DNA markers do not tell any private/sensitive genetic information about the individual. Finally, the majority sees the collection of DNA as the same as fingerprinting.
The dissent, written by Scalia, takes great issue with the majority's argument that the collection of DNA is necessary for identification purposes. In this case, it took Maryland over 4 weeks to process King's DNA. Besides, they did not need to identify him on that basis. Fingerprinting identification is a lot quicker and it is less intrusive in that one cannot learn any sensitive information about the individual as a result. Finally, since King was convicted of the assault, Maryland would have had his DNA anyway. (This is a real quick summary, read the decision for more.)
I am inclined to side with the dissent on this matter. There is no reason for the police to collect the DNA of an individual just because he has been arrested. It is hard to believe you can identify someone based on DNA to make sure you have the right person unless you have a massive database. The State interests the majority cites only becomes an interest because of the collection process. The majority also downplays the intrusiveness of the search. Even if CODIS markers don't reveal sensitive genetic information, it does not mean that authorities don't have that information or that it cannot be found. Simply, an arrest alone should not be a valid reason for the police to collect you DNA and run it through a database.