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Maryland v. King: no big thing

It was all over the news yesterday. The Supreme Court is going to allow the police to take our DNA! They’re going to know everything about us!

Um… not exactly.

Not unless, that is, we happen to get ourselves arrested for a serious crime. Things like murder, rape, first-degree assault, kidnaping, arson, or burglary. (The Legal Genealogist isn’t planning on it. Are you?)

And not unless you’re under the mistaken impression that the DNA test they’re talking about tells the police everything about us. (It doesn’t. Really.)

The reality of yesterday’s decision in the case of Maryland v. King1 is No Big Thing in the world we live in — the world of genetic genealogy.

It literally has nothing — not one single thing — to do with any of us who choose to take DNA tests to help us ferret out our family history, whether it’s our ancestry or our family health history.

What the case was about was the booking procedures police use when a person is arrested for a serious crime. Right now, everywhere in the United States, a person picked up for a crime like murder or rape gets photographed and fingerprinted. And the law allows a search of the person and, under certain circumstances, a search of the person’s immediate vicinity incident to that arrest.

None of this is new. As Justice Anthony Kennedy wrote for the majority:

It is beyond dispute that “probable cause provides legal justification for arresting a person suspected of crime, and for a brief period of detention to take the administrative steps incident to arrest.” … Also uncontested is the “right on the part of the Government, always recognized under English and American law, to search the person of the accused when legally arrested.” … Even in that context, the Court has been clear that individual suspicion is not necessary, because “[t]he constitutionality of a search incident to an arrest does not depend on whether there is any indication that the person arrested possesses weapons or evidence. The fact of a lawful arrest, standing alone, authorizes a search.” …2

The question the Court had to answer in this case was whether the person could also be required to give a DNA sample by way of a cheek swab. And it boiled down, for the majority of the Court, to the fact that:

Police already … use routine and accepted means as varied as comparing the suspect’s booking photograph to sketch artists’ depictions of persons of interest, showing his mugshot to potential witnesses, and of course making a computerized comparison of the arrestee’s fingerprints against electronic databases of known criminals and unsolved crimes. In this respect the only difference between DNA analysis and the accepted use of fingerprint databases is the unparalleled accuracy DNA provides.3

The defendant in the case, Alonzo King, was arrested in 2009 for menacing a group of people with a shotgun. A DNA sample was taken in accordance with Maryland law when he was processed at the police booking station. That sample was sent to the state DNA database where it was determined that it matched evidence from an unsolved 2003 rape case. King was then convicted of the rape.4

Now had King already been convicted for menacing, he would have his DNA taken anyway and it would have been submitted to the database anyway. “All 50 States require the collection of DNA from felony convicts…” And by the time King was arrested, 28 states and the federal government all had “laws authorizing the collection of DNA from some or all arrestees.”5

Moreover, the DNA sample taken from King looked at what are called CODIS markers, after the Congressionally-authorized database supervised by the FBI that holds and reviews DNA profiles from crime scenes and arrestees and convicts. And, the Court explains,

The CODIS database is based on 13 loci … which … make possible extreme accuracy in matching individual samples, with a “random match probability of approximately 1 in 100 trillion (assuming unrelated individuals).” … The CODIS loci are from the non-protein coding junk regions of DNA, and “are not known to have any association with a genetic disease or any other genetic predisposition. Thus, the information in the database is only useful for human identity testing.”6

So… what does this all mean for you and me and our world of genetic genealogy?


Absolutely nothing.

First: The tests we take for genealogy aren’t at all useful to the police database. Our tests tell us how we are like other people — other family members who share common ancestors with us. The CODIS markers focus on parts of the DNA that make us unlike other people and set us apart as individuals.

Second: Our DNA isn’t going to end up in the police database unless we get arrested for a serious crime.

Third: Under many of the DNA-collection laws, even if we do get arrested, our results won’t stay in the police database and any samples remaining after testing will be destroyed if we don’t get convicted. (By the way, that’s not true of fingerprints and mugshots. Those stay in your police file and national databases and can be used at any time for comparison if you’re ever a suspect in another crime.)

In short, once again,7 the DNA privacy sky is not falling.


  1. Maryland v. King, No. 12-207, slip opinion (U.S. Supreme Court, 3 June 2013; PDF of opinion available at U.S. Supreme Court website ( : accessed 3 June 2013).
  2. Ibid., slip op. at 10-11 (citations omitted).
  3. Ibid., slip op. at 12-13.
  4. Ibid., slip op. at 2.
  5. Ibid., slip op. at 7.
  6. Ibid., slip op. at 6.
  7. See also Judy G. Russell, “DNA: the privacy sky is not falling,” The Legal Genealogist, posted 20 Jan 2013 ( : accessed 3 June 2013).
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