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Case shows limits of familial DNA

At first blush, it seems alarming: DNA contributed as part of a genetic genealogy program being used by the police to track down a murder suspect.

LouisianaHardly the use we expect when we do a DNA test to help track down our ancestors and, some might say, an invasion of privacy — even shades of Big Brother!

In reality, the case — involving a New Orleans filmmaker — shows exactly why this isn’t likely to be a common investigative technique by the police, and how in fact DNA testing for genetic genealogy is so different from DNA for police purposes that it really shouldn’t be a reason for anyone to decide not to be tested for genealogy.1

The story ran in the New Orleans Advocate this past week, and you can read it online. The reporter, Jim Mustian, did a pretty good job of explaining just what happened in this case.2

In 1996, a teenager named Angie Dodge was murdered in Idaho Falls, Idaho. The investigation suggested that several attackers were involved, but the evidence didn’t lead to a solid identification of one key suspect — a suspect who left DNA evidence on the scene.

In 2014, the police in Idaho tried something new in their effort to crack this cold case: they compared the YDNA signature of the DNA left at the scene with the publicly available YDNA databases used by genetic genealogists.

They got a partial match — one that cleared the person who had tested but implicated someone somewhere in his family tree, some male relative with a similar YDNA signature — and asked a court to order the genetic testing company to provide them with the name of the person who had tested.

The court gave them the order to get identity of the person tested, and the police then mapped out five generations of males in that family to see if anyone might have ties to the murder. And, they discovered, there were several reasons to look particularly at the son of the man who had tested.

That son — New Orleans filmmaker Michael Usry Jr. — had had reason to be in the area of the murder around the time of the murder. He had sisters attending school there. He had friends who lived there. And he had built a career around making dark films that, according to the news article, often seemed gratuitously violent.

The police then went to a court in New Orleans where Usry lived, and laid out their case. They asked the court to agree that there was probable cause to require Usry to give a DNA sample for testing. Based on all of the factors outlined by the police, the court agreed that Usry should be required to provide a sample.

The news story tells the rest of the tale. Pay special attention to the headline:

New Orleans filmmaker cleared in cold-case murder; false positive highlights limitations of familial DNA searching.3

The test proved, definitively, that Usry wasn’t the source of the DNA sample left at the scene. Quickly, easily, and without any doubt, it cleared him. So the fear some folks have of being falsely accused because of DNA? That’s poppycock. Even in this case where the police had all kinds of other reasons to look at one specific suspect, the DNA cleared him.

But the test proved something else, of importance to our cousins who sometimes fear what could happen if they test for genealogy. It also proved, definitively, why going to genetic genealogy databanks isn’t going to be the first choice of police agencies. Why, in fact, it’s likely to be one of the last choices.

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

And notice that the YDNA alone here wouldn’t have been enough to convince that Louisiana judge to force Usry to test. It was only when the DNA signature was combined with proof that he’d been in the right place at the right time, and more, that there was even an argument that there was probable cause to make him submit to testing.

And if the police do have probable cause to believe that a crime has been committed and that you committed it, they can walk into any judge’s office in this country and get a search warrant that will let them pick you up, trot you down to the nearest medical facility, and take whatever blood or saliva they want for a DNA sample and they’ll use their own lab, not that from a genetic genealogy company, to do the tests they want.

So when that cousin asks you, once again, whether his genetic genealogy test can be used by the police, remind him, once again, that except in really extraordinary cases where the crime is very serious and the police have no clues at all, the chances that the police are going to turn to genealogy DNA databanks are pretty slim.

This Big Easy case shows that using genetic genealogy tests isn’t easy for the police. Our tests are so different from what the police need for a criminal case that, quite frankly, the police don’t particularly want our results — and when they have probable cause to think we’ve committed a crime, they don’t need them.


  1. Unless, of course, you really have committed a crime you don’t want detected, in which case you probably shouldn’t be doing any voluntary DNA testing of any kind. Just sayin’.
  2. Jim Mustian, “New Orleans filmmaker cleared in cold-case murder; false positive highlights limitations of familial DNA searching,” New Orleans Advocate, posted 9 Mar 2015 ( : accessed 14 Mar 2015).
  3. Ibid.
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