When a DNA match … isn’t

Wired reports on a case that should worry us all.

The three men who showed up at Michael Usry’s door last December were unfailingly polite. They told him they were cops investigating a hit-and-run that had occurred a few blocks away, near New Orleans City Park, and they invited Usry to accompany them to a police station so he could answer some questions. Certain that he hadn’t committed any crime, the 36-year-old filmmaker agreed to make the trip.

The situation got weird in the car. As they drove, the cops prodded Usry for details of a 1998 trip he’d taken to Rexburg, Idaho, where two of his sisters later attended college—a detail they’d gleaned by studying his Facebook page. “They were like, ‘We know high school kids do some crazy things—were you drinking? Did you meet anybody?’” Usry recalls. The grilling continued downtown until one of the three men—an FBI agent—told Usry he wanted to swab the inside of Usry’s cheek but wouldn’t explain his reason for doing so, though he emphasized that their warrant meant Usry could not refuse.

The bewildered Usry soon learned that he was a suspect in the 1996 murder of an Idaho Falls teenager named Angie Dodge. Though a man had been convicted of that crime after giving an iffy confession, his DNA didn’t match what was found at the crime scene. Detectives had focused on Usry after running a familial DNA search, a technique that allows investigators to identify suspects who don’t have DNA in a law enforcement database but whose close relatives have had their genetic profiles cataloged. In Usry’s case the crime scene DNA bore numerous similarities to that of Usry’s father, who years earlier had donated a DNA sample to a genealogy project through his Mormon church in Mississippi. That project’s database was later purchased by Ancestry, which made it publicly searchable—a decision that didn’t take into account the possibility that cops might someday use it to hunt for genetic leads.

Usry, whose story was first reported in The New Orleans Advocate, was finally cleared after a nerve-racking 33-day wait—the DNA extracted from his cheek cells didn’t match that of Dodge’s killer, whom detectives still seek. But the fact that he fell under suspicion in the first place is the latest sign that it’s time to set ground rules for familial DNA searching, before misuse of the imperfect technology starts ruining lives.

. . .

… familial DNA searches can generate more noise than signal. “Anyone who knows the science understands that there’s a high rate of false positives,” says Erin Murphy, a New York University law professor … The searches, after all, look for DNA profiles that are similar to the perpetrator’s but by no means identical, a scattershot approach that yields many fruitless leads, and for limited benefit. In the United Kingdom, a 2014 study found that just 17 percent of familial DNA searches “resulted in the identification of a relative of the true offender.”

There’s more at the link.

What’s most worrying about this is that no search warrant was needed to access the familial DNA database.  The police used that warrantless search to get a search warrant that authorized them to take a DNA sample from Mr. Usry.  In other words, a criminal warrant was issued on the basis of incorrect information.

I suspect most of my readers have enough problems with Big Brother, without being willing to tolerate even more overreach by law enforcement.  We need to tighten up our legal system to prevent this sort of thing, otherwise we’re going to be ground under by faceless bureaucrats and their databases that simply don’t care about things like civil rights and liberties.



  1. …we're going to be ground under by faceless bureaucrats and their databases that simply don't care about things like civil rights and liberties.

    Well, maybe, maybe not…..I don't think we've cast votes on this yet.

  2. Back in the 80's the army came to my national guard unit and took DNA swabs of everyone there. The command swore up and down that this would only be used to identify our dead bodies on the battlefield. One year later some congressman made me part of the the largest criminal DNA database in the world!

  3. This case is part of the "CSI effect" where people who have seen how the cops catch criminals using DNA think that the science of this technology is infallible, and judges are susceptible to this, too. If you have ever seen the show, the characters on it have a database for everything, and often solve cases with incredible technological methods. On this show, DNA tests, and searching national databases, take seconds. They often search "gun registration" to see who owns a particular caliber of pistol within two blocks of a crime, or look for all of the red Corollas owned by left handed people, etc.

    No method that is only correct 17% of the time should be good enough to secure a warrant.

  4. …the DNA extracted from his cheek cells didn’t match that of Dodge’s killer…

    That's another problem. DNA cannot determine who killed anyone. A positive DNA match only means, "This DNA pattern matches one that was found at the crime scene". It cannot cay how it got there or if the DNA donor committed any crimes while there.

    So, unless they already know with certainty who the killer is, the statement above cannot be true and is another example of bad crime reporting.

  5. Your statement about a warrantless search shows a basic misunderstanding of search and seizure law.
    The Fourth Amendment does not outlaw warrantless searches; it outlaws UNREASONABLE searches.
    Think of the database as private. There are four ways for the police to enter private property and conduct a search: 1) With a warrant.
    2) With the lawful consent of the owner.
    3) In hot pursuit.
    4)In exigent circumstances.
    Obviously, the database was searched with the owner's lawful consent.
    Mr. genericviews: DNA doesn't float around; it's found in body fluids. Given that the murder victim was a teenage female, it's a pretty good bet that the DNA in this case was found in either blood or semen. Ever hear of circumstantial evidence? If the streets are wet in the morning, that's circumstantial evidence that it rained last night. If a dead body is found and there is blood or semen belonging to another person on or in that body, what does that tell you?

  6. @Old 1811: I don't care if the owner of the database gives consent or not. If my entry into that database was conditional upon the owner's guarantee of privacy (which, if you read the article, it was in this case), and the database is then sold to another owner who refuses to honor that guarantee, of what use is it?

    No. My information is, and should remain, my own. I disagree with any system that allows third parties to trade in it for profit or law enforcemtn without my approval. (And yes, I know that this principle, if enshrined in law, would overturn a great deal of the US economy. Good.)

  7. "…just 17 percent of familial DNA searches “resulted in the identification of a relative of the true offender.”"

    Hmm. I wonder. Does this statistic include searches that gave no match at all, or such tenuous matches that a warrant wasn't sought?

  8. When you give your information to a third party, it is no longer your property. It's the property of the third party. The third party is obligated to take reasonable precautions to insure the privacy of that information, but that's it.
    I'm not saying there should be no safeguards. I was just explaining the law regarding searching of private databases. If the owner of that database wishes to require a subpoena (not a warrant; warrants are for things or people; subpoenas are for documents or information) to search that database for information, they can do so.

  9. That is just scary but very believable.

    I was on a bone marrow donor list. I assume now that is public too since I am past the age of being able to donate marrow.

  10. The VA asked me other veterans to give them our DNA for "research" I refused. The VA is part of the U.S. Government so I don't trust it.

  11. Mr. genericviews: DNA doesn't float around; it's found in body fluids. Given that the murder victim was a teenage female, it's a pretty good bet that the DNA in this case was found in either blood or semen. Ever hear of circumstantial evidence? If the streets are wet in the morning, that's circumstantial evidence that it rained last night. If a dead body is found and there is blood or semen belonging to another person on or in that body, what does that tell you?

    Or in skin cells, which can be brush transferred from innocent me to not so innocent you if we shake hands, or if my bare arm brushes your clothing on a crowded subway.
    You then deposit both DNAs at the scene when you commit a crime. Proof positive that innocent me was there; no doubt as your accomplice. Too bad we're not under 24/7 surveillance wherever we go. That would clear me, I guess.


    "On one occasion, I swabbed my own hand after handshakes at a social function to determine the presence of other epithelial cells. The laboratory was able to obtain a mixture of my DNA as well as two other individuals."

    This couldn't incriminate someone innocent. Right?

  12. Skin cells aren't collected at crime scenes. Body fluids are.
    If you're gonna be paranoid, there are enough real things to be paranoid about. You don't have to make up new ones.

  13. All I did was explain the law and the way investigations work. I didn't know you were into shooting the messenger.
    I'm done here, and I'm never coming back. I don't go where I'm not welcome.

  14. old 1811. I am not arguing the technology. I am arguing the logic. A successful match only means "there is a pattern match between the sample from the crime scene and the pattern obtained from the suspect".

    It is up to the investigators and prosecutors to connect the dots about how that DNA pattern came to be there and it's significance WRT any crimes being committed.

    I can tell you for a fact that my home is chock full of my DNA. Anyone collecting fluids in my house would likely also collect skin, hair, boogers and other body debris (despite my best efforts at cleanliness). These samples would be intermingled with other family members who live with me and my pets. Likewise with my car. And my office. and my clothing that I drop off at the dry cleaners, that gets mixed in with everyone else's dirty laundry before being returned to me. fluids are used because they provide the best chance of getting an uncontaminated sample. This is not about paranoia. Follow the logic.

    DNA by itself cannot convict anyone of anything, circumstantial or not. Nor can it demonstrate innocence. All it can say is These two samples match, or they do not match. All other inferences after that must be proved by other means.

  15. Similar to finding a fingerprint at a crime scene. It doesn't prove that I committed a crime while there, nor does it prove that I was ever there at the crime scene at all. All finding my fingerprint at a crime scene proves is that I once touched the object that my print was found on.

  16. and to add: I have a real problem with the police using agents to secure information and evidence that they could not otherwise obtain. For example:

    1 The police want to search your home. You have a maid, and she has instructions to never allow anyone into the home. A cop asks your maid to search your home, and she lets them in, in exchange for a cash award.

    2 You agree to back up your information with an online, cloud service. In the process, the service agrees to keep your information private. The cloud service is presented with a letter from the FBI, asking to see all computer information in their possession. The company then freely allows the FBI to access that information, which they use to compile a firearms registration database.

    I have a problem with both of those scenarios. How is this any different than the company disclosing your DNA, even though there is a confidentiality agreement? This is the exact reason why lawyers, spouses, clergy, and doctors have historically been subject to confidentiality exceptions to the law. You have to be able to confide in some people and entities in order to live your life. It feels more and more like a police state every day.

  17. Part of the problem is that too few people really understand the basis behind DNA evidence. It's not as hard and fast as many imagine.

    Case in point: Chimeras. There are people out there who have more than one cell line, with differing genetic information in different parts of their bodies. We don't know what the prevalence of this is, in the general population, but it could be fairly high.

    The case of Linda Fairchild is instructive. The state asked her to prove the paternity of her two children after applying for public assistance. DNA tests confirmed that the father was who she said he was, but that she was not the mother. Cue several years of legal troubles for Ms. Fairchild, as she was accused of illegal surrogacy and welfare fraud, until testing confirmed that she was a tetragametic chimera, meaning that her cells derived from two separate lines, likely the result of two sperm implanting two eggs in her mother's womb, and then combining for whatever reason into one embryo. We don't know enough about the hows and whys of this to answer questions, but it does show that the chances of DNA evidence not being as conclusive as we once thought is there. Imagine a rapist, cleared of rape because his buccal cheek swab doesn't match the sperm taken from his victim–When, in fact, he just has a different set of germ cells from the rest of his body. Such things have happened, as witness the unfortunate Ms. Fairchild.

    Frankly, I think one step we ought to be taking is to compare like tissues to like tissues–If your evidence is based on blood, check the blood, if on skin, check skin cells. Semen? Compare to semen…

    Mark my words–In a few short years, we're going to be looking back at the current uses of DNA in evidence as being something just slightly short of witch-doctery. I would wager that there are people out there who have been exonerated from their crimes, and who were completely guilty, as well as men and women who were convicted on erroneous DNA evidence that was misconstrued, falsified, or just plain mistaken.

  18. Having been on the other side of this, it can be assured that once access to a database has been granted through subpoena, should the investigating party itself perform the search there is absolutely nothing in that database which will not be discovered and subsequently examined.

    Proprietors of databases are very busy people, and short cuts are a way of life; with disturbing frequency (disturbing for those whose data resides in the database) subpoena response is a full copy of the database, or at least access to all of it. A few of those and it can be determined not just what your shoe size is but the name and date of birth of the second cousin of the cobbler who made them.

    The Supreme Court ruled decades ago that trash placed at the curb is no longer yours to control but belongs to whomever wants it – "trash pulls" by law enforcement are not at all infrequent. I suspect we're at the beginning of similarly performed "data pulls", not to mention the threat from extra-legal hackers (side note: I've wondered why entrepreneural hackers haven't entered the "I'll find that for you" business as sub-contractors to investigative organizations. Then again, perhaps they have).

    If you have information you want restricted, once you release it – any of it, no matter how small or insignificant (think credit card use or driving past a traffic camera) – from your custody, custody meaning "direct, complete and consistent control," you've forfeited your opportunity to prevent its dissemination regardless of the proclimations to the contrary by the data recipient or storage operator.

    Why anyone with two functioning brain cells would put even the smallest amount of their data in the "cloud" completely escapes me; securely physically locked up and extremely well encrypted is now the rule of the day. As another side note, SCOTUS ruled some time back (or it might have been a federal appeals court and SCOTUS cert was denied, I can't remember, and the result is the same) it is not illegal to use an alias as long as there is no intent to commit fraud. Just sayin'…..

  19. AAARGH. "Proclamations" not "proclimations". I need either a new keyboard or new fingers….I know, I'll turn "autocorrect" on. That'll take care of it……

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