> What prosecutors did not disclose is that genetic material from the rape kit was first sent to FamilyTreeDNA, which created a DNA profile and allowed law enforcement to set up a fake account to search for matching customers. When that produced only distant leads, a civilian geneticist working with investigators uploaded the forensic profile to MyHeritage. It was the MyHeritage search that identified the close relative who helped break the case.

Basically they send in the genetic material and create an account on the site, then see which relatives it matches with and go from there.