I think it is something to do with Mitochondrial DNA within the body part found. Teeth are excellent repositories for this sort of stuff.
The DNA tests from crime scenes work somewhat differently to match up people to evidence, or otherwise.
If someone took a sample of your bone marrow and gave it to a lab they can discover all sorts of things about you like hair colour, eye colour, racial origin etc. However they can't make a picture of you from it.
Science is amazing and I'm sure this data is correct as they know which parts of the genome form eye colour etc. So statements like that would be accurate.
At a crime scene they'd just have tissue to work from not Mitochondrial DNA, however this can be matched to a person in the same way a fingerprint can.
Are you sure that the Cops are not pulling your leg, and getting you to admit to a crime, even tho' innocent, 'cos you have no way of disproving the DNA stuff!...

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Them: "Trust us. We know what we are doing"...

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Us: "Its a fair cop, Guv!"....

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..Magic....a bit like brain surgery, pocket-watch repairing, fixing the brakes on your car, etc...
Paul...You can fool most of the people...most of the time...

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