Fitzpatrick had co-authored *Forensic Genealogy*, published in 2005, and had co-founded Identifinders International with Andy Yeiser, formally established in 2011. She had developed expertise in applying genetic genealogy methods — the use of DNA database matches to identify unknown individuals or unknown relatives — to cases where traditional investigative methods had reached their limits. The Lori Ruff case was exactly the kind of problem that forensic genetic genealogy was emerging to address.
When Fitzpatrick read the Seattle Times article in June 2013, she contacted Joe Velling and offered to work on the case. Velling, who was at an impasse, agreed.
The forensic genetic genealogy method that Fitzpatrick applied does not work in the way that crime scene DNA identification works. It is not a direct match against a database of known individuals. Instead, it exploits the large consumer DNA databases — Ancestry.com, 23andMe, and others — that millions of people have uploaded their genetic data to voluntarily, often in search of information about their ancestry or distant relatives. These databases contain not the DNA of criminals or missing persons but the DNA of ordinary people who wanted to know more about where their families came from.
The method works because DNA is shared among relatives. A second cousin shares approximately three to four percent of their DNA with you, on average. A third cousin shares approximately one percent. The shared segments, while small, are detectable through analysis of hundreds of thousands of genetic positions across the genome, and when a match appears in a database, it suggests a family connection that can then be pursued through traditional genealogical research.