How is DNA used to identify a suspect?

July 14, 2024 11:37 AM

Very curious about the law enforcement logistics of a recent news story.

According to the FBI, Thomas Crooks was not carrying ID, so investigators used DNA to identify him (BBC). But Crooks had no police record record (ABC). "They analyzed his DNA to provide a biometric confirmation of his identity," (ABC). The FBI released his name in under 8 hours. How did they identify him so quickly?
(Deep condolences to the victims, and not seeking any partisan discussion, of course!)

posted by nouvelle-personne to Science & Nature (9 answers total)

Pure speculation, but I would assume that one of his biological parents or siblings was in the system, the system returned a partial match to a close relative, and they went from there. Or he had personally done a DNA test that fed into a database that law enforcement is permitted to query.
posted by moosetracks at 11:52 AM on July 14 [7 favorites]

All the for-profit DNA companies rat to data clearinghouses and law enforcement, plus various carceral systems force the collection of biometric data. So all it really takes is a cousin or two in prison and/or 23andme anymore. (You can get a better idea of where all this data can come from if you look at articles related to the capture of the Golden State Killer.)

But it's also equally possible that this is an easy lie and the actual story will come out weeks or months from now, including whether that's even the person in question. Under 8 hours is a very surprising turnaround even in a high profile case. I'm not reading any of the news at this point, knowing most of it will be bunk before maybe Tuesday or Wednesday or several years from now.
posted by Lyn Never at 12:21 PM on July 14 [6 favorites]

The military takes DNA, too. A person shooting at a Secret Service protectee has the highest law enforcement priority, so this test would have jumped to the front of any line. Hsi family likely gave or would be willing to give DNA. Can only imagine their distress.
posted by theora55 at 12:50 PM on July 14 [1 favorite]

Best answer: The family might have provided some hair from a brush, or his toothbrush, or something else that could carry his genetic material.
posted by chesty_a_arthur at 1:01 PM on July 14 [3 favorites]

Best answer: I've seen reports that the gun was registered to his father, so they zeroed in on the right person quickly but had to confirm.
posted by I claim sanctuary at 1:52 PM on July 14 [2 favorites]

If he drove there they found his car somewhere nearby in that rural area and identified him by that. If someone else drove him there the plot thickens.
posted by mareli at 2:27 PM on July 14

Best answer: I wouldn't necessarily trust any early reporting on this, it's still very early in the investigation. Note that one article says he was identified by DNA, the other says his identity was confirmed with DNA.

My speculation is that the FBI meant the second one. He may not have ID on him but he did have a gun and a vehicle, both have registration information, accessing this registration information is faster than DNA processing.

If truly all they had was DNA, as others have said, there would be methods to trace him from family members, but I don't think these can be accomplished from sample to answer in 8 hours.
posted by muddgirl at 3:30 PM on July 14 [4 favorites]

It might also be lousy journalism, and the person was identified by, as others had said, car, weapon, or fingerprints (you know that "fun" trip you took to the police station in kindergarten where they tried to take your fingerprints? Yeah.... ).
posted by Dotty at 6:00 AM on July 15 [1 favorite]

Before there were more details, I wondered if the swift DNA ID might have tied to Jan. 6th-related collections of DNA samples. [According to an analysis done last year, "Pennsylvania ranks third among U.S. states for the total number of residents charged with Jan. 6-related offenses."]
posted by Iris Gambol at 11:43 AM on July 15