Quote:
Originally Posted by retiredguy123
I heard on TV that he was tracked down using "ancestrial DNA" which means that they can identify someone who has no DNA stored in the Federal database. I don't know much about DNA, but I am skeptical that this would be possible, unless they had knowledge of who his relatives are.
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The DNA of the suspect's relatives is alike in many aspects (but not in its entirety). If one of these relatives (i.e. mother, father, brother, sister, etc.) has their DNA on file it is a simple matter to compare crime-scene DNA to the DNA of these relatives and narrow down the field of suspects to just a few candidates. Subsequent police work (i.e. verifying candidate's whereabouts) can then usually eliminate all but a prime suspect. The police don't necessarily need to know the suspect's relatives, since they can easily search our very broad DNA data base for matches.