The process produced a large population of possible candidates, then a smaller one, as the tree work narrowed. Investigators applied additional filtering criteria: the behavioral profile of the East Area Rapist suggested someone with a background in law enforcement or the military. The evidence of deliberate operational planning suggested someone organized and methodical. Predictions about ethnic heritage from the DNA evidence pointed toward European, including possible Italian, ancestry.
Through months of work, the investigative team identified Joseph James DeAngelo as a candidate. He fit the age range. He had lived in California during the relevant period. He had a background in law enforcement. He had graduated from high school in the Sacramento area and had later returned to the area. He was on the list of candidates that the genealogical work had produced.
He was not yet identified as the person responsible. He was one of several candidates, and a genealogical match is not proof of guilt in any legal sense. What the genetic and genealogical work had produced was a lead — a specific named individual who warranted investigative attention and who would require independent corroboration before investigators could move further.
Corroboration: The Discarded DNA
The standard approach to corroborating a suspect identified through investigative genetic genealogy involves obtaining a DNA sample from the suspect through a method that does not require their knowledge or cooperation. In practice, this typically means obtaining discarded material — something the person has used and left in a public location or in trash that has been abandoned.