The suspect left his DNA at the crime scene. Collection of DNA samples is a routine task at crime scenes. The police went to a public web site, GEDMatch and compared the suspect DNA with their database and identified possible close relatives. Those relatives had provided their own DNA to GEDMatch using the DNA sample that they had obtained from Ancestry or one of the other commercial DNA analysis companies. This is a common activity among people who are using DNA to find relatives. GEDMatch is a free site. Unless you or your twin brother is a murderer, this is unlikely to have an effect on GEDMatch, who have probably enjoyed free publicity from stories like this.
Thanks for clarifying — I wasn’t sure of the mechanics of the search/match process.
That still is quite a chilling scenario. That my BROTHER’s DNA could be matched to a crime scene and then used against me is disturbing.
But you bring up a VERY interesting point. If people know their DNA can be gotten without subpoena and then match to crimes it could kill the DNA analysis industry.
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It’s impossible to avoid at this time. You may never be sampled but relatives will give a strong match and you can bet they will be in the database.