Rae-Venter began working formally with the investigative team in October 2017. The DNA profile she was working with had been developed from biological evidence preserved from multiple crime scenes, with the Ventura County rape kit evidence providing material for the genealogy database upload.
The choice of GEDmatch as the database reflected its particular features. GEDmatch accepted uploads of raw DNA data files from commercial testing services — 23andMe, AncestryDNA, MyHeritage, and others export downloadable raw data files to their users, and those files can be uploaded to GEDmatch for comparison against other users’ files. GEDmatch also allowed comparison of uploaded files against all other profiles in the database, regardless of which commercial service the original test came from. This cross-platform comparison capability made it more comprehensive than any individual commercial database.
The crime-scene DNA profile was not originally formatted as a consumer genealogy raw data file. Translating a forensic DNA profile — developed using CODIS methodology, based on short tandem repeat analysis — into the format used by genealogy databases required specific technical work. The format used by genealogy databases is based on single-nucleotide polymorphism analysis, a different approach that produces data compatible with the comparison algorithms these databases use.
A laboratory conducted the necessary conversion and analysis. The profile uploaded to GEDmatch was a genomic profile derived from the crime-scene material, formatted for compatibility with the genealogy platform’s comparison systems.
The database returned matches — individuals whose uploaded profiles shared DNA segments with the uploaded crime-scene profile. The matches were distant. The closest matches were identified in contemporaneous reporting as third cousins or fourth cousins — individuals who share a common ancestor with the person who left DNA at the crime scene, but at a genealogical remove of three or four generations.